I had to replace the Killer wifi card with an Intel card, as the OEM one was flaky and this seemed to be a known issue that wasn't acknowledged by Dell.
The battery failed on me 3 times, and I eventually gave up on the warranty and bought a third party battery which I installed myself.
The power connector got loose, which required replacing the motherboard.
The case itself is not very stiff, so putting it over the edge of a knee or table means the touch pad won't click due to the flex.
Perhaps newer models have addressed these sorts of issues, but I'd be wary of buying another considering the Thinkpad I got for work has been very solid.