I'm typing this on a 3 year old e-machine bought from PC World - Intel Celeron 733Mhz!!! - and the only thing that has gone wrong was due to the RAM when I upgraded it. The new memory stick was faulty. The engineer just took it out and the machine was fine again. Obviously they are built to a price and the component spec isn't top notch. But decide what you want to use it for what your budget is first. If you don't need state of the art kit, and aren't into serious gaming, then an e-machine could very well make sense.
Having said all that, there are some great deals on other systems out there. Get hold of one of this months computer mags and trawl through the ads to see what I mean.
Good luck with whatever you buy.