Efficiency: 9-12 pods, depending on valve/settings. I've seen some get more, but that's what I'd bank on.
Maintenance: Very little to do, and you don't have to do it often. There's no high-end out there that's easier to maintain.
Rammer: It moves the bolt and opens the valve to release air and accelerate the paintball. In the image below it is the silver moving part above "PBPORTAL.DE"
If you have a tight budget I'd check out the etek3 or 4. They are going for as low as $175 pretty regularly, and will likely be in much better condition than a comparable 07.