The ssd will speed up access, especially to larger files, but once you are in the game, it only helps for smoother playing instead of the occasional little stutter that can sometimes happen when it is loading files.
The speed of the ssd for this purpose is next to irrelevant if you are using sata 3 as the speed it loads at is more than enough to keep play back smooth, so you could save yourself some money or put it towards a larger drive eg a crucial SSD for around the same price.
I have tried this on several different SSD drives, and unless you are loading a ridiculously large map and textures then there is no discernible difference you will notice.
At the end of the day though the choice is still yours to make. Just make sure you do your research into reliability of the drives and manufacturers, and all will be well.