While OS X 10.7 Lion is just around the corner, a number of people running older Intel Macs that came with OS X 10.5 Leopard or even 10.4 Tiger installed have written in wondering whether they should upgrade to the latest current release of OS X, version 10.6 Snow Leopard. Apple offers Snow Leopard upgrade DVDs for $29, but despite this relatively cheap price the decision to upgrade will depend on your uses. Here are some things to think about to help make the decision.
Upgrading from Snow Leopard to Lion will likely be easier
This is just speculation on my part since Apple has not released any specific system and OS requirements for upgrading to OS X 10.7, but if you are planning on upgrading to OS X 10.7 when it is released, you might consider upgrading your current installation to OS X 10.6. Though it is likely Apple will support upgrading from OS X 10.5, there is better chance that Apple will not support an upgrade from OS X 10.4.
At the very least we know Apple will support upgrading from OS X 10.6, and since currently you can upgrade from OS X 10.4 to OS X 10.6, doing so will better prepare your system for an upgrade to OS X 10.7. Again, this is merely speculation for now. One option is if you have an available OS X 10.6 installation DVD, then you can just keep it around, and if OS X 10.7 will not directly upgrade an OS X 10.4 installation, you can then use the Snow Leopard upgrade DVD to bridge the upgrade to 10.7.
You may not install Lion right away
While you might be considering bypassing Snow Leopard for Lion, keep in mind that the initial release of OS X 10.7 may have a few bugs to iron out. A good recommendation is to allow others to test the features of the new OS out first before upgrading. This means that if you upgrade to OS X 10.6 now, then you may still use it for a good six months or so before finally upgrading to OS X 10.7.
Snow Leopard is the same as Leopard
Are you a MobileMe user? Upgrade!
The OS features in OS X 10.6 may not be of much use to some people, but if you use MobileMe services then even if you are running OS X 10.5 you will benefit from upgrading to OS X 10.6. Apple is migrating away from supporting older OS X versions with its online services, and if you regularly use these services then upgrading your OS to the latest version will help. On May 5, Apple will be upgrading its MobileMe calendar, which will not be fully supported on OS X 10.5 and earlier.