As far as I understand it, an SSD will only provide a slight improvement in loading times for games, because of the faster disk access times over traditional mechanical disks coupled with the higher read/write speeds.
The difference is not as pronounced with gaming as it is for the overall improvement it makes to Windows. I do recall seeing comparisons before (probably on here) and the difference in loading of games between levels was around 2-3 seconds in most cases. For Windows in general, it totally transforms the user experience.
In regards to your monitor's response time, the move to a SSD doesn't really have any impact. You should consider more if a 3ms of 5ms monitor would have more of an impact than any drive update (short answer: Not really.)
While the new drive would be able to access playfield data more quickly, it still takes "substantially" longer for your video card to render the image. Consider the fact that a high-end video card may have as much as 1GB of super fast DDR5 memory on board just for rendering graphics. That cache memory is FAR faster than the memory in a SSD, and the video card has no trouble keeping up.
As for the $70 Vertex, that's a nice deal, but it would be a serious disappointment if "performance" is your ultimate goal. It's a SATA-II drive, which will deliver about half the performance of a SATA-III drive. I recommend checking lots of benchmarks and comparisons before you buy. Never has "you get what you pay for" applied to anything more than SSD's.