I disagree with Randolph's Answer. If anything, the article says exactly the opposite of the "good performance for a while" part.
What we found was the exact opposite: an OS that doesn't appear to be affected by SSD performance degradation
And I don't have Apple's SSD. I have an OWC on a Mac Pro and haven't had any performance degradation since I brought it, about six month ago. Before that, I had an Intel drive and also never had degradation problems under OSX. I changed the drive because my 1st drive was too small. That Intel-M drive is running on a laptop with Windows 7 Home Premium.
So far, it has been proven that OS X doesn't suffer from the lack of TRIM support; what we don't know if that's because the OS/FileSystem is doing something different or because there's TRIM support hidden and not reported.
In any case, getting a SSD is really a performance increase. I only use it for the OS and some minor things, the rest sits on a mirrored SATA RAID, but this is a Mac Pro, so things are different.
On small Macbooks, the usage of SSD is like day and night and I haven't seen performance degradation over the course of a Year.
Maybe there is one, but if that's the case, it's so slow that by the time is significant, you'll be either changing the drive or the whole computer.
I've been using SSD since late 2009.
I recommend you don't get one from Apple, as they tend to overcharge. Get one of the many SSD's alternatives like Corsairs, Intels or the OWC I have, which I heavily recommend.
But the SSD market is in a constant evolution, so read before you buy.