10.0 is a huge step up from 9, and although I haven't used it, the talk at my full time job is that CS is incredible. i'm just waiting for them to buy a bulk license for it. you might not have an option though. they might not be producing the 10.0 upgrade anymore. adobe is funny like that sometimes. i'm sure 9 is upgradable to CS though.
Any previous version of Illustrator is upgradeable to the newest one, currently Illustrator CS. I have Adobe Illustrator 7 and mainly use it to get vector paths into Photoshop. I also use Macromedia Freehand 10 and CorelDRAW 9. Lately, I've been getting more and more AI-CS generated PDFs from customers. Some will open in Illustrator 7 and others will not. It is likely I'll upgrade my personal licenses soon.
There hasn't been any official announcement yet, but Adobe is due release their next version of the Adobe Creative Suite. The product annoucement could come sometime in March. I'm hoping the software will be shipping by May. Acrobat 7 is one of the first applications in the suite, and its updated PDF technology lays down some of the foundation for the next versions of Illustrator and InDesign. The word is the applications are supposed to be a good bit faster in performance.
Another possible wrinkle in the Adobe CS2 launch is Microsoft's pending launch of WindowsXP Pro 64-bit edition. There's already one 64-bit version of Windows made for Intel Itanium CPUs, but with Intel's rollout of the PentiumIV 600 cpu series and their upcoming dual-core "Smithfield" processors, everything is starting the transition to 64-bit.
Why would Adobe delay things to recompile code for 64-bit? RAM limits. Currently, Adobe Photoshop cannot allocate anymore than 2GB of RAM. 32-bit computing limits you to 4GB of RAM, 2GB for the OS and 2GB for the application you're running. 64-bit will allow applications to use almost limitless amounts of RAM.
Migrating to a 64-bit version of Windows may be tricky. Legacy software and periphreals may not get along with it. You need new 64-bit device drivers for everything from scanners to mice. Software installers need to be at least 32-bit coded. Some sign design applications still use 16-bit installers and lots of chunks of 16-bit code. They will not work on a 64-bit OS. Also, many of those dongles we have to use for apps like Flexi, EnRoute, Neon Wizard, SignLab, etc. will need new Rainbow or HASP drivers.
Anyway, the point is be careful about jumping into that 64-bit thing. The next Adobe Studio CS version should be along shortly and could possibly even be 64-bit.
The Mac versions of Adobe's products are all 32-bit. None are coded for 64-bit. When it comes to both Mac and PC software, very little has any 64-bit stuff in it.
Sure, the MacOS has some big chunks recompiled to handle 64-bit software. However, the OS is mainly tuned to handle 32-bit stuff. It has to do that. Otherwise you wind up with a "server only" solution like Intel's Itanium platform where if you want 64-bit EPIC coded apps, device drivers, etc., you're going to have to write them yourself. Not too bad a deal if you own a Fortune 500 company with a top flight IT and development department.
A few PC games have 64-bit coding chunks to take advantage of certain AMD processors. Those functions are making specially designed direct calls to hardware, not really anything based on the OS itself.
Certain flavors of Linux, Sun Solaris, IBM's AIX, etc. operate in 64-bit mode, but just like Intel's Itanium line (and the 64-bit version of WindowsXP specifically made for Itanium CPUs), you are usually stuck with only running 64-bit software and hardware on them. For most computer users that situation would really stink.
For now, the whole 64-bit thing is a very overrated thing. The only real advantage any regular end user will get out of it is stuffing a computer with more than 4GB of RAM. That much RAM is still pretty darned expensive.
Even if WindowsXP 64-bit Edition ships in March (the version written for regular Intel Pentium and Xeon CPUs), I won't be looking at loading it on any PC I have anytime soon. Until all the apps I use are recompiled for 64-bit (especially those with antiquated security dongles), I'll consider 64-bit more of a liability than a plus.
Just thought I'd point that out to prevent this from turning into some silly Mac versus PC thread. Applications, such as Flexi or Photoshop, are the only thing that actually matters in that game.