After having had 3 iPods fail (one right out of the box) I got tired of their high failure rate and looked around at other players. I bought the Sansa last July and have been quite pleased with it. The Sansa has received fairly high marks in various reviews. The sound is quite good for an MP3 player; just as good as the iPod. The only downside is that there are few accessories for it. Don't use it to store pictures and so I can't comment on how well it performs in that area. But for music it's great and so far has been more reliable than the iPod.
It's also worthwhile buying alternate headphones / earbuds as the ones that come with the Sansa (or the iPod for that matter) are simply not very good. I bought Shure e4c and it was truly a night and day difference from those that came with the Sansa (or the iPod). May not want to invest that much money in a set (they cost more than the Sansa) but their lower less costly models are also a definite improvement over the stock cords that come with the players. Seinhausers are also worth investigating.