The reason fragmentation slows down a standard hard drive is the average latency, or the average time it takes to reposistion the heads for reading in a new location.
framgented drives have to move the heads more often than unfragmented drives thus slowing down the read or write process.
there are other problems with a regular hard drive fragmentation in that the directory structure or the mapping of where the file fragments on the disk reside also have to be read to find out where to get the fragments.

I find it hard to believe that an SSD drive would be that bothered by fragmentation mainly because there is latency or no time required to move the heads around.
the only thing that should be a minor problem is that it takes multiple read commands to find the fragmented data.

I didn't buy an SSD drive before because a lot of reviews from actual users showed that many of the first SSD drives had serious write delays causing short term system lockups meaning the SSD was slower than a regular drive
however these Intel drives seem to have this fixed, at least I haven't seen anything like this.
the SSD are silent and VERY cool to the touch while my hard drives make at least some noise and get pretty warm to the touch.