I have a Ryobi battery-powered mower. My lawn is maybe 1000sqft and the battery has just enough juice to get it done. I think it has a smaller capacity battery than the Black & Decker, but it works well. It even has a 5 year warranty, which includes the battery.
Prior to the Ryobi, I used a cheap corded mower. Dragging that cord around, making sure it didn't get hung up on stuff, then having to wrap the cord back up....I'm much happier with the battery-powered mower.
I say go reel mower. They are actually lighter and easier to push than a powered mower. You do need to keep actual grass growing though. Reel mowers don't go through stalky weeds and stuff good, they just leave them standing.
X2 ! The exercise is good as well, unless you let the grass grow really long, then you'll work your butt off cutting it.