Useless especially when they have price markups on the hardware that are significantly higher than $200 with price markups well over $1000 when you go for a gaming PC that can actually game.
the $700 x51 is only a gaming PC if you consider playing farmville to be gaming, or if you consider yourself to b a retro gamer and don't plan to ever go to anything harder to run than half life 2.
it is also not a standard form factor so upgrading will be difficult, especially since it comes with a 240 watt power supply, so even if you manage to get a high end GPU that is still low profile, it would would likely not run.
their $700 system is the equivalent to building yourself a $350-400 PC, whats more crazy, at $1100 all you get is a lower mid range gaming PC with a GTX 760