You certainly have a good system and your graphics card even though it is older appears to be up to spec
Your system is similar in many regards to mine. I am having zero issues with video or sluggishness. Behaves near identical to Nuendo 7.
Have you tried knocking out the video files right out of the Project, saving it out, rebooting the app and open the file again to see, if that is the issue?
-Andrew
Quite sluggish GUI response here on Windows 10 compared to Nuendo 7.0.
Do you have a graphics card that can run OpenGL 2.0 or are you using integrated graphics off the Motherboard?
Hello heisenberg9,
The sluggishness is gone already if you read all the posts, this was simply a matter of an Nvidia graphic card update.
My issue is with N8 freezing every once in a while, sometimes very often, at other times every 20/30 secs.
I´m still working on a solution, the issue is even apparent with an empty sequence, with no plugins or audio-video.
Thanks for your advice
I have ATI Radeon HD 7950 in my Mac Pro 5.1 12-core … And also performs sluggish… What to do in that case??
I’d say update the drivers…
Sorry, but there is no any other ATI Radeon HD 7950 for MAC drivers such as in macOS.
ATI 5770 vs ATI 7950 in the same Mac Pro 12-core 5.1:
I think it’s 3 fps … 
Disaster.
Unfortunately, it does not appear to be a sticky in the forums but it is essential for Steinberg and the Users if they are trying to figure out what is going wrong and track bugs that you place the details of your computer setup in your signature. Your essential hardware and OS at a minimum. Such as…
Type of Motherboard (or prebuilt computer name and model), the CPU model number, amount of RAM, type of video card with amount of VRAM, the OS version & service packs if applicable.
This thread as case in point. People are focusing on the video card but it could very well be the OS that is at root of the problem. How is anyone to know? Please take the time to do it so people’s time is not wasted and a quicker resolution can be found rather than continually questioning people about their setup.
For me, N8 performance is basically identical to N7. Running Nvidia video driving one 4K monitor and one 1080. Rest of specs are in my sig. All good here in terms of snappy GUI on N8.
Maybe on Windows … but not on MAC.
So confirmed two people running Windows 7, 64 bit with NVIDIA cards have Nuendo 8 running smoothly.
Still no issues with my system.
OK. I have an almost prehistoric Cheesegrater Mac Pro 1,1 that came with an ATI 5770. Think that machine came out in 2006. I tried to run Premiere Pro on it back then which requires CUDA to run. I don’t think OpenGL 2.0 was around then. The card completely choked on Premiere Pro. I upgraded with a newer card that ran CUDA (similar to OpenGL). The new video engine in Nuendo 8 appears to require OpenGL 2.0 compatibility based on the minimum specs. Have you checked to see if the 5770 meets the minimum specs? I am betting it doesn’t.
hello from Cubase user 
we have same problem in C9, and Steinberg already knows about that problem, and working on fix.
for MacOS users its more critical then for WinOS: [CAN-6382]Mac users with GUI/graphics issue. - Cubase - Steinberg Forums
also tread with all GUI bug’s and glitches, and some fixes: [CAN-6382]Mac users with GUI/graphics issue. - Cubase - Steinberg Forums
Pretty sure Cubase-Nuendo have same GUI bugs
The sluggish performance was easily solved here by updating my Nvidia cards drivers.
Config: Windows 7 SP1, HP Z820 2x Xeon E5-2670 Cpu, 64Gb ram, 3x Nvidia Quadro fx1800 cards.
But I still can’t get N8 to work properly, I have regular “freeze-ups” of the system, cursor stops, N8 is silent, all meters freeze and after 20-30 secs its starts running again skipping those 20-30 secs.
Tried a lot of things already, including thrashing prefs and starting from zero, removing plugins etc.
I’ll wait for the next update to see if things improve…if they don’t I might have to try a whole fresh install for Windows, although I don’t see the point as N7 performs just fine!
Thanks for your help linzevalk, but it didn’t help.
As C9pro has the same issue with some users, theres is hope they will come up with a solution soon.
Have you tried removing two of the three video cards to see if that is the problem. You also have a 2 CPU machine. Theoretically, you should be fine but Steinberg mentions in a support note that the DAW goes erratic with over 14 cores active on Windows 10. Here is the note:
Just thought of something else, your Quadro card issues 10 bit video whereas GeForce is 8 bit. I wonder if Steinberg tested their new video engine on Quadro cards?
Ditto, same here: no real issues to speak of (or that weren’t already niggles in N7). N8 performs a little better with the same N7 prefs, ASIO settings etc. Opens and plays all earlier N7 & C9 projects Some with quite large VI dependencies; a dozen or so with large vids). Works the same me (so far), but now with a nicer Cubase skin … Oh, at one point after the N8 install I did some major work with reconfiguring & relocating all of the PCIe cards (six) given that I fitted a new Dell TB2 card & which required one particular PCIe slot. No problems there either with N8, and certainly far less so than many other aspects of Win10 dependencies. I’ve also had to re-instate various restore points at times, again, no real issues there. Perhaps some of the problems listed in this thread could do with a clean Windows install?
My only real SB winge is with Absolute 3 installs which have a mind of their own & never seem to get it quite right it terms of knowing that all sample libraries are located on a dedicated SSD. HALion 6 for example still errors in finding some of its various sounds … Ditto its dumb library manager. Odd that it doesn’t already reference a preference to where things are (like Native Instruments for example) but that’s another story and a different set of bugs.
Have you tried removing two of the three video cards to see if that is the problem. You also have a 2 CPU machine. Theoretically, you should be fine but Steinberg mentions in a support note that the DAW goes erratic with over 14 cores active on Windows 10. Here is the note:
Just thought of something else, your Quadro card issues 10 bit video whereas GeForce is 8 bit. I wonder if Steinberg tested their new video engine on Quadro cards?[/quote]
I can’t imagine it being the issue, N7 runs just fine with 3 (10bit) video cards, that should also be possible with N8…
The core issue I know of, but I’m running W7, so that doesn’t change anything either…
I guess it’s just some cleaning up in the programming (I hope), otherwise I’ll stick with N7 (waste of money than) or change DAWS in the future…I work a lot with ProTools too, so that would work, but I like Nuendo’s workflow and midi facilities.
Nuendo 8.0.15 didn’t change a thing, still the DAW freezes up, this version seems to be even buggier…I hope they find a way to get it working for me…
Nuendo 7 still runs fine…gladly, I’m not using the new video engine before I’m sure of it’s potential…