When it comes to USB 3 media readers, I have found they can be significantly faster, and I've never had corrupt files myself. When it comes to updating a conventional HD to SSD, it's pretty easy now. You can get USB 3 adapters to plug a new SSD to USB 3, then mirror your current main HD to the SSD, then install and make it your main drive.
I also mirror other responses that the OS and apps installed on a SSD are the main speed advantage. I've got one laptop that has a 250GB SSD and 750GB HD. With it, I have my apps and OS on the SSD: and try to have 80GB free for cache/swap files. I keep my Lightroom catalogues in the default directory, and my RAWs stay on the HD (I've always tried keeping my HDs 7200 RPM). If the program in question is Lightroom, I think another potential slowdown is how big your catalogue is. I've heard folks complain about things really slowing down when they have really large catalogues. I'll create new catalogues for each "roll" of images I have.