I did the same thing... and it was great. I added a 128GB SSD, but unfortunately, I needed more space for media and work files (large datasets). So, I ended up removing the DVD drive and replaced it with the old hard drive. I never need the DVD drive outside of the house, so this ended up working great for me.
I'm planning on doing the same thing with my Macbook when the new Intel 24nm SSD's come out in Q4 '10 or Q1 '11. The new drives will bring down prices on the 128GB drive to <$200.
For me, media files were a killer too, so I simply put my media collection on an external HDD, "cached" my favorite 20GB or so of content on my SSD (the stuff I put on my iPhone, essentially), and started relying more on streaming services like Pandora, Rdio, and Hulu, etc.
I did this in July and I haven't used the external drive even once...
