I've just installed a Crucial M500 480Gb SSD in my mid 2007 iMac (2133). Everything went flawlessly and the guides on iFixit were very clear and helpful. Because of the different drive size (2.5inch) I bought the Newertech AdaptaDrive 2.5" to 3.5" Drive Converter Bracket in a Dutch online store. It took me about 45 minutes to open up the iMac, remove the HDD, install the SSD en to close the whole thing again. Removing the LCD display is actually the 'hardest' part because you don't want your 'greasy and sweaty' fingers on it. In the end, it all seemed simple and straightforward. I'm now running Lion with 4Gb RAM, the 480 Gb SSD and TRIM enabled; my iMac feels like new. The disk speeds are roughly 4,5 times faster than the original HDD.