I'd appreciate them sending the correct battery... The battery at the top is the one my computer shipped with (56Wh and rounded). The bottom battery is what they sent me initially (53Wh and square).
It took another day for them to finally come through with a battery I could use. This battery works the way I expect. Despite using the wireless or wired internet for research and typing, the corrected battery lasted about 2.5 hours. My guess is under a "class" load (occasionally typing notes, wireless off, sitting idle otherwise w/background processes terminated) this machine could last for 3 or more hours.
Moral of the story: Dell does it right, eventually.