I have been running a 17″ i7 Macbook Pro since it was release earlier this year. Ever since I got it I have been waiting for the price of SSD’s to come down so I could swap out the 500Gb hard drive with an SSD drive and put the 500Gb drive into the optical bay.
Yesterday my 120Gb OCZ Vortex 2E SSD drive was delivered and all I can say is WOW, this thing is fast. OSX now boots in just over 10 seconds and Photoshop launches in 3 seconds flat! This thing is EPIC!
SSD drives are amazingly fast but the price is quite high so the best way to configure the system is to have your Operating System on the SSD drive along with you applications, then have your home directory (profile) on the normal hard drive. This means you can load your original hard drive up with your massive video and picture files, while using the SSD drive for things that will really benefit from the speed.
If you are really short of memory (RAM) then it is always worth upgrading, but providing you have a relatively modern computer (with a decent disk controller) then an SSD drive is far and away the best bang for the buck!