I landed the Marc Pro but I've used the Compex system. They are definitely different but both work wonders. I'd suggest using the Marc Pro pad placement as they optimized theirs for recovery and waste flushing. You can find the manual here
and I've had other Compex users state they prefer these placements as well.
For me I focus on my glutes to stimulate them firing, calves, quads, hamstrings and the shoulder region. I would say I use it week in and week out 3-5 hours easily. I have a desk job so I just pump my legs for a couple hours in different groups throughout the day. I'd say it's given me a bit more bounce in my stride and I feel a bit fresher but that could be in my head. The real advantage was "teaching" certain muscles to fire and for that reason alone I'm happy with the purchase.
"Train so you have no regrets @ the finish line"