Hi, I feel you with your questions, a lot of people are in the same boat. My personal opinion and plan for dealing with this to stick with 1.5 for now. Last I read, 1.5 will be supported until at least mid 2012, meaning they should offer some sort of upgrade path to 1.8. Who knows how complicated it will be, 1.8 doesn't exist yet so there is no way to know.
Bottom line for me is that 1.5 works and is compatible with everything, I have clients to think of and it just has to work. Unless you have a very specific reason to upgrade, I would let the dust clear a bit before doing so. Again, just my opinion.
The difficult we do immediately, the impossible takes a little longer.