The Pro edition, which costs $20 more, adds secure data wiping, data recovery, a firewall, and antivirus protection, though I didn't test the latter two. I found version 7.5 intuitive and a bit easier to use than previous installments. Users who wish to know exactly what is being done and why won't be disappointed; the program also offers complete and extremely granular explanations of each action to come. In fact, perusing System Mechanic's help file is an educational experience that might be worth the price of admission in and of itself.
Over the years, I've used System Mechanic mostly for recovering data and wiping hard drives, but the tune-up features have also worked well for me. That brings me to my only caveat about the non-pro version: Much of what the tune-up portion of the program does is automate tasks that an advanced Windows user (or your geeky friend) will already know how to perform manually using built-in Windows utilities.