Since updating to OS 10.5, I have not used the Chemdraw 9.1 program on my computer. Shortly after updating to Leopard, I downloaded a demo version of Chemdraw 11.0 just for the fun of it, and used that for 2 weeks. I didn't really intend on purchasing it since version 9 does everything I needed.
Well, the two week trial ended and I reverted back to Chemdraw 9.1. Everything was great until I tried to save my file. Apparently, while using OS 10.5, Chemdraw 9.1 can't save. I got the spinning wheel and then Chemdraw would quit. I tried everything. Uninstall, install, repeat.
Eventually, I had a choice. Go back to 10.4 or buy Chemdraw 11.0. Well, like they say, once you go 10.5 you never go back (or something like that). I asked my IT friend if they would foot the bill. They said yes. Apparently, the $270 for software is nothing in the grand scheme of IT. So, I now have Chemdraw 11.0.
Since I am a Mac guy and since Cambridge Software is slowly becoming more and more Mac-unfriendly, I purchased the Chemdraw Pro version of 11.0 since the Ultra version contains lots and lots of cool features that work only on a Windows machine.
For how I use it, I have not noticed any big changes or improvements. The interface looks nicer, but the functionality is essentially the same (at least for how I use it).
The one thing I really wish they would include is a shortcut button for the "distribute" function. I use this all of the time. When I have a number of structures, I like them distributed evenly. The "center" and align functions all have shortcut buttons, but not the distribute. Unless there is some way to set this up, I will always be annoyed by this shortfall.
I'm also annoyed by the fact that in all of my installing and uninstalling and upgrading, I forgot to save my stationary files (i.e. document settings). Which means, I'll need to recreate these someday. Oh well, that was my fault. I had different settings for exams, reports, and other things. I hate the ACS document settings for use on exams. The nice thing is, version 11 has Wiley settings which are very close to what I use for exams.
 The $270 is the upgrade price for Chemdraw Pro with the educator discount.