I'll echo Ryan. Stihl or Husqvarna, from a local dealer, not the Borg. The dealer can provide advice and service that is worth the extra money spent by shopping at the little guy's place. When I bought my Stihl, I went to a dealer that sold both (plus Echo and a few others) and asked for his recommendation. He told me both were great saws, but most of the local pros were using Stihl chainsaws, and that he had a better, faster parts supply line with Stihl than with Husqvarna. He also said that in other parts of the country the story could be the exact opposite, with Husqvarna being the better choice. As a side note, a couple of years later I wanted a pro-level string trimmer, and I went to the same shop, planning to buy a Stihl. The dealer talked me into an Echo instead, citing the same reasons he used when he talked me into the Stihl chainsaw. That trimmer is another one of my "makes me smile every time I use it" tools, just like my chainsaw.
I'll also second Ryan's recommendation to spend a bit more money and get model that's in a grade above the low-end consumer levels. In the long run, it'll save you money, and you'll thank yourself every time you use the saw. My first chainsaw was a Poulan from Home Depot. It worked OK for about a year, but it was a chore to use and eventually got to where it was hard to keep running. So I dropped about $600 on a Stihl MS390 and have had no regrets at all. Here again, I went with the dealer's advice for help in pickout out the model. I explained my needs, and he suggested the MS series -- Stihl's mid-grade line. It was the biggest engine in that line, and about $150 less than the same-sized pro model. The dealer said that for my frequency of use, the mid-line would still last me a lifetime, and unless I really wanted the few ounces lighter weight that the pro line offered, I should use the extra money on something else (like protective gear). I equipped it with both a 18" and a 24" bar. I should never have to replace it in my life, and it just simply works when I need it to. And man, will it eat wood.