I've been happy with my Ryobi that I bought last year. Then again, I'm (at best) a rather irregular user of it. Once my "major" project (redoing the floors) was done, the saw accumulated stuff the same way every other flat surface in my garage does. You know, tools, lube cans, auto stuff. But it definitely cuts straight, and even the mitres are good enough for cutting baseboards @ a 45 degree angle.
If you think you'll be using it a _lot_, get something better, though. But for the price/performance for infrequent use, the Ryobi is great.