I just ordered a 550XP for $534.99 delivered(from eBay). It has a 20" bar; a little longer than I would have liked, but there is the old-guy bad back thing to think about! Should have it by the end of next week. And I put the 445 on Craigslist...someone's coming to pick it up tomorrow, with a "back-up" buyer waiting in the wings.
I only want one saw, so it has to be both (a) light, and (b) powerful. I did a lot of reading up on Husky saws, and thought that the 550's autotune feature has been around just long enough to prove itself. I am looking forward to using the new saw on a stand of trees I need gone. I will post up the results once I run a few tanks of fuel through the saw and get a feel for how it does.