If you have an Intel Mac of any sort and you’ve been waiting to install 10.6, now is a good time. There is always the chance that something that you use will not be compatible with 10.6, but if you make a backup first (please) you’ll be able to revert to 10.5. There’s a good list of compatible/not compatible programs at Macintouch.com– worth your time to check it out.
It is always better to download the “Combo Update” (linked above) rather than a simple Software Update. So do it that way if you can. In fact, if you already did the Software Update, download the 10.6.2 Combo update and run it.
Given the advantages of 10.6 over 10.5, and the super-low cost ($29), upgrading to Snow Leopard (10.6) is a smart move. The only question really was when to do it. With 10.6.2’s fixes in hand, the time to upgrade is now.
If you don’t have a Snow Leopard disc you can buy Snow Leopard from Amazon.