Lots of these look great on paper (specs, features), but they're not though out well. For instance the mainboard can be a serious bottleneck if not matched well, cooling might be an issue (case design) and power consumption (if you care about it).
That's funny, considering that I have 10 eMachines that I bought 4 years ago running 24x7 server tasks without any problems.
Yes, cooling can be an issue if you put a 100 watt graphics card and overclock the crap out of everything.
Joe the Plumber, however, thinks that "overclock" is when you get paid more because you work more than 40 hours per week.
He's not going to see these issues from any mainstream vendor's system.