Usually it helps when you purchase games from psn, then entire game is saved on HDD and for this reason it's worth it. But when you purchase games on Disc then only small amount of data required to run game is installed on HDD. And that part is already prepared be loaded fast as it could be.
If you're asking whether or not it'll help, the answer is yes, it will, if you're playing something that accesses the hard drive a lot.
If you're asking whether or not you should, the answer is no.
My understanding is that the storage device isn't the bottleneck, it's the PS3's data transfer rate. In that case, the speed benefit of an SSD is only in the seek time; a mechanical hard drive has to spin the platter to the right place to find the block containing the data it needs to load, but an SSD can access any memory address directly, so the seek time is consistently fast but the difference is hardly staggering. Once located, though, the data will transfer from storage to the PS3's processors and/or RAM at more or less the same MB per second rate, whatever it is, because a fast hard drive will be able to match the PS3's data rate.
I think it might make a difference in a PS4, though...
An ssd is only marginally faster for most games and ssd's are still more expensive than regular hdd's.
That's the reason why I chose to swap my original 40 GB hdd with another hdd instead of an ssd.