We are VERY excited about Apple's new OS. However, our suggestion for business users is the same as it has ever been. If you have business critical computers and software... WAIT AT LEAST A WEEK before you install any major OS upgrade.
Case in point, we use Daylite in our business and they have contacted their customers asking them to do exactly this... to wait. In their blog post they mention that until just recently their software was working fine in pre-release versions of Lion. But something changed last minute and now they suggest that users wait. We agree whole heartedly.
If you are a home user and run nothing but Apple software, you are likely safe in upgrading immediately. For the rest of us, we suggest you wait a week. If you need to be cutting edge and see the latest thing, go check out the new Harry Potter movie at the midnight showing this week and brag about being first for that instead of Lion.
Long story short, my experience is that most software vendors will have their patches out within a week of the release. So wait to feed the Lions for a bit and your transition will be much smoother.
Take care and have a great day.