Im not sure exactly what you mean by there being a big hit in performance? The increase in RAM, simply put, allows you to open ever larger projects, use more and more instruments or plug in effects, without the system slowing. Indeed a 64bit system would typically be significantly faster. It makes sense therefore that workflow too should be increased. 32 bit had a limit as to how much RAM it could make use of (4gb), and so as the demands of modern software and its capabilities grow, the RAM restrictions imposed by 32 bit architecture become ever more of a limitation if not a barrier. 64bit can cater for significantly larger amounts of RAM.
About the only real hindrance to a 32bit-64bit transition, as far as Cubase is concerned, is backwards compatibility. IE - getting your 32 bit plugins n VSTs to still work in the 64bit environment. Whilst Cubase does offer a bridging solution, this is by no means a perfect solution to the problem. 32bit plugs are likely to crash in a 64bit world. Whilst other 3rd party companies, such a Jbridge, do to some extent offer a better bridging solution, this whole idea of making 32 bit plugs ins which work seamlessly within the 64bit environment is simply not there just yet (if indeed it ever will be). And even when it does, the old 4gb RAM restriction will still apply for these plug ins. For that reason most VST instrument/plug in manufacturers offer two versions of their software. One 32bit and one 64 bit. Allowing the user flexibility and choice as to how best set up their system during this transitional period.