We're a Dell house so I really ought to enthusiastically agree with the posters supporting Dell, but the reality is that all of the professionally built servers (HP, Dell, IBM) are well put together and should last for years.
Supermicro are an interesting case, as it very much depends on who puts them together. The components are good, as plenty will attest to. And there are some excellent Supermicro server builders out there who will build product every bit as good as the big guys, but there are also some servers out there which are, how shall I say, less than optimal. Go with a recognised and recommended builder with a credible warranty and it should be fine, go with the cheapest and it's more of a gamble.