SSD's are awesome. I can't imagine going back to having a HDD as my OS drive.
You can boot into Windows in approximately 10 seconds. Can format and install a fresh copy of Windows from a thumb drive in under 10 minutes.
As far as my graphic design and editing OMFG the difference is even more noticeable. Applying filters on huge graphics is instantaneous, its great.
I got the Crucial M4 128GB because at the time the Sandforce controller was having some serious issues. There was so many horror stories blowing up everywhere online I completely avoided it. I imagine that is no longer an issue though. Just make sure you do your research on which one to get.