So, in preparation for Mountain Lion, I'm going to replace my hdd with a Crucial m4 256 gb SSD and leave the RAM at 4 gb (for now).
People who have replaced their hdds with a ssd, will I see an improvement?
You should 1st do the RAM upgrade and then the SSD. *gb will also avoid swapping to disk and will protect the SSD from excessive writes. I would personally do 128GB SSD + 8GB instead of 256GB SSD.
I had the same MBP and I had 8GB RAM and 120GB SSD and it took the same time to boot and load programs as my current 15" quad core MBP 15 with 512GB SSD and 16GB RAM!