My first boss (i'm a tree surgeon by the way), once told me that Husqies are the ferrarri's of saws, great when they work, but require alot of maintenence. Sthil are more like volvos, not quite a good but keep going. The Echo's now are becoming a supurb saw. Makita's are great, but run at very high revs (good for clean cuts and fast work, but not so long lived). Jhonserad are low budget husqies (same company), so very good and very little difference.
Go with the best you can afford, but don't be tempted by bells and whistles.
And, as everybody has said, get yourself on a basic chainsaw course as soon as possible (most farm colleges offer them). And make sure you get the best protective gear possible (most accidents are by inexperienced users, cross cutting and not wearing ballistic trousers).
Good luck and feel free to ask for any advice
Baggins