I work in PS/LR daily for my job and I really wasn't that excited about CS4, I still use CS3 on my laptop and I hate to say it, I like CS3 better - its more stable for me.
Generally in business you have to be careful taking leaps of faith into software upgrades, especially while in the middle of unfinished projects. However, being in this industry, when our outside vendors and freelancers upgrade, we have little choice but to comply and face the upgrade path with fingers crossed. Then still wind up using the very same tools and filters that gets work done. So here we go again, and my CS4 installation disk hasn't even cooled off yet.