Here's a very good article about SSD's
http://www.anandtech.com/storage/showdoc.aspx?i=3531&p=1
The main advantage of SSD is that there's no delay when accessing data scattered across the disk. In conventional drives it takes time to put the head in correct place and start reading, while in SSD you just ask and get what you want. It's not several times faster, it's orders of magnitude faster. Writing performance is not as good due to some SSD mechanics, but it's still on par with conventional drives. Defragmenting is not needed, because data is accessed immediately no matter where it is. And it only wears hard drive because of unneeded moving and writing data to another place.
This makes SSD very good drive for system and frequently used programs. Applications start much faster, you can launch several programs at once without delays even immediately after system boot.
Another advantage is grater sequential read speed, which is about 2 times faster than conventional drives, actually peaking the bandwith of SATA II connection. This makes loading large files into memory faster and decreases loading times of games, which have to load large amounts of data (mainly textures) into memory.
Except shortened loading times, games don't benefit much from SSD, because they don't use data directly from hard disk in general, and are designed to work well with conventional drives. Everything needed immediately is first loaded into RAM when the game starts, and then extra chunks of data are loaded in the background, so that possible delays don't affect gameplay.
I also plan to buy SSD in the future, probably something from Intel X25-M G2 line, but I don't expect miracles in FSX. When FSX loads, it uses CPU more than hard disk, (unless we have very big photoscenery) so I wouldn't expect very big improvements in loading times unless we have at least quad core CPU. But it should make aircraft selection list to show up almost immediately, and help with loading textures lag when switching views.