I read, after having problems with the first replacement drive, that it's pot luck with cheap DVD drives - whether the optics are really correctly aligned is anyone's guess. In my case, the drive occasionally read a Wii disk, but would usually cause an error on returning from a game to reading from the disk again. The signal that it failed to read a disk at all was a series of drive startup sounds, each followed by a loud click - I guess the optics failing to find something on the disk, retrying, and eventually returning to park position.
The only other thing I noticed is that the drive data cable can easily become bent when you reassemble the device. The kink in the data cable of our device did not prevent the second drive from working correctly. But I could imagine that a wire could be broken by such a kink.
Thanks - really great! Had to try twice, because the first replacement DVD drive was also bad. Only problem - I don't think that the front panel wires can be unplugged on my device. Eventually just left the front panel attached by it's wires. Parts and tools ordering over the web site is a real help as well.