They are certainly well worth it, I bought one about a month ago for my PC and was so impressed by it I went ahead and bought one for my laptop as well. My laptop is silent 100% of the time, no vibrating, no fans, nothing. Boot times with windows are around 20 seconds, and on my laptop running ubuntu is about 10 seconds. Power downs are almost instant, and virus scans take like 1 minute to do a full scan.
They've dropped in price quite a bit, and they finally becoming more mainstream. I'd personally wait until you can find one no sale, as they seem to go on sale for a very reasonable price, but its up to you.
I have windows running on a 40gb one, and that seems large enough as long as I make sure everything saves onto my 1TB HDD, otherwise the 40gb would fill up fast. My laptop is running ubuntu on a 60gb SSD, which seems to be enough. If not I'll pop this one into my PC and by my laptop a 128gb one.