I think this is the best cache plugin (and it's free!) for WordPress hands-down. Quick Cache is the only caching plugin that supports full caching across all devices (mobile, tablet, desktop, etc.). It is both very effective and fast, but also simple to use. You just turn it on, and it works. No complex options to set.
Yes, it requires PHP 5.3 or better. Yes, it will break your site if you don't have the proper requirements. That's why you're supposed to install upgrades in a test environment before going live with it so you can work out any of the possible problems that may occur. It took a couple of work arounds on my sites to get it right with the upgraded version before I went live with it.