I downloaded H4 as an updated of Halion Sonic on Saturday. As I’ve never owned any of its predecessors (H1-H3) I can’t say anything about how it has progressed, but the look of H4 indeed impresses me. It’s too early to throw the dice but at first glance I can’t imagine not liking H4 in another month, after getting to know to it. It seems complex… in a good way 
What are your first impressions and personal experience?
I’ve had it a few days now… via the download option and i’m stunned with it!
I had an old Casio FZ1 years ago which anyone who remembers them will know was one hell of a machine… pretty much the most sophisticated sampler of its day! It really was a fantastic machine but notoriously tricky to use…
I can see a lot of the facilities in H4 that were present in the FZ1 only on a much larger scale and MUCH more developed, as well as things like flex phrasing, reconfigurability, sonic complexity, the inbuilt mixer etc etc… the sound quality is phenomenal too IMHO!
I’ve only spent 2 or 3 days with it using it in a couple of projects and whilst it is a bit of a beast i’m finding it pretty straight forward to get around and use… to be honest it’s probably a little overkill in some areas for my needs but in terms of sound creation and for various nifty production tricks it’s perfect for my needs!
Some of us older guys used to look at bits of kit like the classic Fairlight CMI years ago… some of us were lucky enough to know someone who had one, but next to this it looks like a pocket calculator!
The included sound sets are fantastic IMHO too… certainly PLENTY of sounds included that got my creative juices flowing very quickly!
If you have HS already but you don’t need a sampler then i wouldn’t bother with it but for the £83:00 it cost for the upgrade, again for my uses it was a VERY attractive deal!
Only gripe i can really think of is that it won’t load AKAI format samples which is a bit of a shame… any chance in a future update?
apart from that i am REALLY pleased with it…
I haven’t had the time to dig any deeper into it. Can only say that it looks impressive. My initial idea is for a big part to use H4 as a sound creating tool, making my own patches.
One thing I need to take a closer look at is how to use the “auto mapping” when importing multiple samples at once. I didn’t figure that out yesterday when importing rhodes samples consisting of three different velocity layers. No matter what I tried the samples allways ended up being mapped totally wrong. I suspect that this is due to my own lack of understanding 
Thank GOD I read this post before purchasing Halion 4. I would have been devastated to have the spent the money and found this out later. I downloaded the Halion 4 manual just to confirm and sure enough, no Akai support. How lame. I have tons of Akai CD’s from 15 years ago that are phenomenal to this very day that I now have to give up because Halion 4 decides to cater to WAV format only? I will be keeping my Halion 4 money to put towards other things now.