Here are the minimum specifications Apple has for Snow Leopard.
- Mac computer with an Intel processor
- 1GB of memory
- 5GB of available disk space
- DVD drive for installation
- Some features require a compatible Internet service provider; fees may apply.
- Some features require Apple's MobileMeservice; fees and terms apply.
I am running 10.5.8 on my Mac. But I need to upgrade to 10.6.8 to use iCloud with my new IPhone 4S. Can I update? If so, will it affect existing software? Affect anything else negatively? Is there a downside? thanks
Yes, it likely will affect some software; here's a list of applications and how compliant they are with SL;
Any PPC apps you're using will need Rosetta; it's installed by default in Leopard, but you may have to select it in the additional installations when installing SL.
Other stuff includes printer and (especially) scanner drivers. Check the vendor for updates, and/or Support Downloads for the latest drivers.
Otherwise, SL is pretty well OK. I wouldn't say it was dramatically better than Leopard though.