I picked up one of these a few days ago to complement a newer Sandy Bridge setup. For no reason I could ever figure out, my boot times were terrible with the motherboard (an Asus P8P67 Pro) using a conventional HD - on the order of 3 minutes from cold until the PC was responsive. Connected to a SATA-3 controller, this SSD reduced my boot time to around 35 seconds, and, once the desktop appears, the PC is fully responsive to whatever you want to do. It sounds obvious, but the main thing that differentiates SSDs from conventional HDs is this "snappiness" factor - seek times are completely flat, thus, the only delay is actually transferring data off the drive to RAM for CPU operations (and this drive is capable of >400 megabyte per second bursts). The drive is also completely silent, and it's slightly weird not to hear the usual HD ticking & clicking. You may also need a 3.5" drive bay adapter; physically, the drive is about 50% bigger than a credit card and very light - alternatively, I have seen these drives held in place by double-sided tape - with no moving parts, you can pretty much put them anywhere the data and power cables will stretch. Also, a side effect of the "solid state" part of the drive is that it is largely unaffected by any movements or accidental drops - anything that doesn't destroy the casing will leave the drive completely unaffected - the interior is largely the same as a USB flash drive, but with larger capacity chips and a small controller.

I initially had some trouble with the drive (some stuttering and pausing) after installing Windows7 then Intel's RST drivers (the drive is connected to an Intel ICH9 port), and decided that a re-format would be my best option to completely get rid of the Intel drivers. When installing Windows only takes 12 minutes - and at that, you're largely limited to your DVD drive's transfer rate more than anything else, it's no longer a chore, and using Win7's built-in ACHI drivers fixed the problem completely.

There's also a little more to installing one of these compared with a standard HD. You should connect it to a SATA-3 drive port to get best performance (although it will remain very fast if you're using a SATA-2 port on older motherboards). You also need to run the Windows Experience Index in Windows7 (and in fact, use Windows7 too, since it contains drive control commands optimised for SSDs not found in older versions of Windows). When Windows has run the Windows Experience Index, it will fully recognise the drive as an SSD and automatically disable some scheduled processes like defragmentation etc. Lastly you can check your speeds are what they should be with e.g. AS SSD Benchmark - sequential reads should be over 300 or 400 megabytes per second depending on the controller you're using, and if so, you're good to go.

Obviously, the downsides to this drive are the high cost and relatively small capacity; at 120GB after formatting, a default installation of Windows7 itself will immediately eat another 17GB or so, so you're basically looking at 100GB all told once you're set up. While smaller applications like web-browsers etc. load more or less instantly now, more extensive applications show less benefit - e.g. a modern multi-gigabyte game will only show speed differences of a couple of seconds. In all, it's a mixed bag, but, I could see myself abandoning conventional HDs in the future as prices come down over time. If you need very large quantities of storage space, you won't want to use these, but 100GB is minimally useful for a working system plus a few apps. And of course, you can continue to use any existing HDs you have for secondary storage.

EDIT : Been running this drive for slightly over a year now with no real ill effects, although I am finding the 128gb quite cramped now with the addition of a Dropbox account (weirdly, even though the Dropbox folder is on another, larger drive). A minor speed-bump was the firmware update Crucial sent out late last year where unless installed, the drive would reboot itself after (x) thousand hours of use. As a bonus, however, once you have the update installed, you get an extra 100mb/sec speed boost, so it's not all bad - although the bug would effectively prevent you from using your PC for more than an hour at a time.

Since I bought this, prices have roughly halved, and I'm strongly considering getting another one of these in the 256GB flavour to complement the existing one.