Shauhncy,
My 2007 iMac was running badly with Yosemite (it was being crippled by long periods of mysterious disc activity). So yesterday I put a Crucial 512GB MX100 SSD in and it's made a big difference and I'm more than happy with the results... delighted in fact. I'm going to upgrade the memory at some point too (4GB -> 6GB)... that should do me for a while longer. So, yes I'd say it's worth upgrading to an ssd but I think you definitely need to upgrade the ram to at least 4GB min.
b e n