I thought I would recap my experiences and maybe it may help some of you. Some of this I have posted in other threads - so I'll try to keep it as brief as possible. I initially was upgraded from a 24" to a 27" via Applecare because of a HDD failure, among other problems. My problems with the 24" started at the beginning of Nov., that week I took my iMac to the store and back 4 times. I dealt with some flaky Apple reps who didn't return my calls or emails, and finally reached a couple who would. I could go into detail here..but I'll leave it at that. I first opted to pay an extra $300 on my replacement, to upgrade to the i5. I received it after 2 weeks, restored from my SL backup - and the hard drive grinding noises began. It was pretty constant, so I swapped it out. Apple upgraded me to an i7 because of the problems discussed. I had read the HD threads and noticed many people were experiencing problems with the Seagate 1 TB drive. I asked if there was a way they could ensure I didn't get the Seagate, but they couldn't. And I did. And the grinding was back. An Apple rep told me to try restoring my computer completely by creating a new partition (he said he preferred this because it reset boot settings) and installing the OS. He didn't want me to install my files. So I did. The HD noises were faintly there, but not nearly as bad. Then I restored from my TM backup, minus the "Settings" portion. The noises were more apparent again. I was upgraded to a 2TB after being escalated up the food chain (again), and explaining the issues many users were having. I received the 2 TB machine last Friday. It is much quieter. I don't notice the grinding noises very much at all, it isn't silent but I couldn't even focus with the 1 TB drives. I have seen a couple weird things happen though. For example, this morning my screen saver was inexplicably changed from Arabesque to Flurry. I didn't change it. Another example - I put a DVD in last night, and it wouldn't eject. I had to restart the computer. This happened on one of my other replacements too. My 24" issues started with weird screen saver problems (not activating, etc.) Putting this together with the grinding noises being more apparent when files were restored...I really am worried that restoring like this creates conflicts with settings or pref. or some type of system files. For all those wondering, I haven't done the 'yellow' test. My first 27" did have a very apparent tinge, however. I am keeping this iMac. I don't want to go through the hassle again. If I were buying a new iMac, I may not say the same thing though. If I could wait, I probably would. But since I was upgraded it's not as big of an issue. I'm more worried about the TM restore files. Hope this may be helpful for some of you.