There are too many posts to read in this thread, so I apologize if I am repeating anything.
The cracks on the emachines hinges are structural, not superficial. Apparently they are pretty common on emachines (well, generally it's a much more common thing with any brand these days)
I have a M6805. Mine developed cracks within the first 6 months, but remained cracks for awhile. In November, 18 months after purchase, the cracks became gaping holes in the hinges (both sides). Looking in there you can see that there is just this little metal assembly that keeps the lid on the unit. At that time, the monitor was very lose and would fall backwards with the slightest touch. You also had to have the lid opened in just the right spot or the LCD would turn off. The other problem that started with the holes in the hinges was that the computer would shut off randomly. Sometimes when it got hot, and sometimes when you just turn it on and it hasn't even loaded windows yet. Sometimes it would shutoff, and then immediately shut off when restarted for at least 10-20 minutes. (so basically I couldn't use it for awhile) Within a few weeks of that point, the monitor just came completely off the hinge.
(this could in general be an indication of what will happen to an eMachine when the hinge problem progresses...)
I have a Best Buy service plan, which came in handy. As much as I hate Best Buy, it is essential to buy some kind of extended service plan with a laptop, especially an emachines. Best Buy put on a brand new LCD, which is great because I had a dozen or so bad pixels on the old LCD. Compared to the old one, the new one makes this seem like a brand new laptop. And speaking of new laptops, it's cheaper for Best Buy to pay the claim on the service plan to buy a new computer, than it is to buy me a new LCD (their PSP invoice says they paid almost $700)...never makes sense to me. I divert, but in my experience Best Buy will fight to the dire end with their replacement policy...
Anyway, all I wanted to add is that the cracks are definitely structural, but if you take care of it after cracks develop, you have a shot at it working great for quite a while longer.
Moral of the story, don't buy an emachines, or at least don't buy an emachines without an extended service plan. They're cheap and you get allot for your money (all proprietary parts though), so as long as you get the ext. service and don't mind losing your computer for 2-3 weeks every so often they could be worth the savings. I only have 512 MB of 2700 DDR, and it flies with the 1.8 MHz AMD64, even while under heavy use with dozens of windows open. It isn't very mobile, however, with its big size, but that isn't a big deal.
The other point I intended on making is that I have heard of people that see cracks in the hinges of their emachines just weeks after buying them. Don't think it's just a superficial thing; take it back right away and get it exchanged. (assuming this is still within the return period)
Damn this turned into a long email... (sorry)