10.6 upgrade to Lion or Mountain Lion dilemma

Apple designed OS X 10.8 to be directly upgradeable from OS X 10.6.8. The only reason I can see to go to OS X 10.7 is to see if you like the changes Apple introduced, which were further refined (depending on your point of view) in OS X 10.8.

One thing you might consider doing, which is what I did when I migrated to OS X 10.7 is to create a dual boot system. I initially installed OS X 10.7 on an external hard drive until I was comfortable with it. I then created a partition on my internal hard drive for OS X 10.7, and copied it in when I was ready to make it my everyday OS X. I retained a partition with OS X 10.6 as there are one or two programs I use that won't run under Lion. The dual boot setup works well. You could go directly to a dual boot/partition system if you don't have an external hard drive available, too.

WIth either Lion or Mountain Lion, while 2GB is the minimum, 4GB is recommended. And the system will run a little faster (3% to 5%) if you have matched memory, ie, 2 x 2GB memory cards, due to the Intel architecture.

Early 2009 machine?

It's nearly 4 years old and in it's end of life stage.

My advice is keep it on the faster Snow Leopard and not risk breaking your machine with a incompatible firmware update (requires a expensive logicboard repalcement) by upgrading to 10.8, especially if your out of AppleCare.

If you want to upgrade, now is the time to get 10.8 on a new machine and ease into it. (even selling the 2009 Mac before it dies)

The "dual boot" solution is not ideal, 10.8 will change the GUID and add another hidden partition, which will make it impossible to fix from the 10.6 install disks, you choice with a serious problem will be to erase the entire drive from the 10.6 disks. Also it will tie the machine to you, 10.8 can't be transfered to a new owner, it will have to go back to 10.6

All in all there is very little benefit to go to 10.8, a lot of risk and of course your PPC based software will not function in 10.8

For instance, Adobe is allowing free CS2 right here basically, but 10.8 users can't run it.

https://www.adobe.com/downloads/cs2_downloads/index.html

I'm keeping 10.6 on my Early 2011 17", and gradually easing myself into Windows 7 as it will get security updates and support until 2020.

I now favor stability over chaos, it's just costing me too many gray hairs and much money with broken hardware flipping the OS over every year like Apple wants.

My last 15" died when Lion firmware was applied, I got no compensation from Apple as it was out of AppleCare, turns out Cupertino HQ was pwned by Flashback bothnet at the time and likely had a lot to do with my machine failing because it ran just fine under 10.6

If you want a change, then do it on new hardware, that way if you don't like it you can return it or sell it and fall back on old reliable Snow Leopard.