Anyone who might be able to tell you is under a non disclosure
agreement with Apple. In other words: there are no known problems with
using BBEdit on Lion, at least not outside the group of people who might
know but cannot tell you.
Given the experience with BareBones in the past - with previous system
updates - I do not anticipate strange (computer hopping across the desk,
jumping screen first into garbage can) things to happen. Or if they
happen, it'll probably be fixed before Lion ships, so you never know it
could have happened.
Maarten