I have one. Got the video card replaced a couple of years ago under a special Apple extended warranty, other than that, no issues. Upgraded to 20 GB RAM, and just recently decided to swap out the original 1TB hard drive with a SSD. Took about 20 minutes to do myself, and it feels like a whole new machine. Now it runs so fast, quieter and way cooler. Still a beast and should be good for quite a few years to come.
The adaptor was included in the OWC SSD kit I purchased specifically for this computer. Must say it works flawlessly. Computer is barely warm now - this thing used to really heat up with the optical hard drive.
you can keep the internal hard drive and add the ssd as an extra drive underneath the optical drive. this is what I do, no sensors needed, and you can use the spinner for time machine backup, data storage etc.