Actually, just ordered mine (D800, without the e) - I will have it on Tuesday and can't wait. And yes, a spare battery is part of my initial purchase too, plus two 32Gb Lexar 800x CFs funny enough.
Regarding card speed - that is not my worry. I won't use this camera for work where fps is relevant (never had) - it is just the consumption of memory and processing speed for images that will never be printed bigger then A4 that is my concern. To address that I may, for example occasionally switch the D800 in 'eco'-DX mode (yet NEF!) for the snapshots. I surely need a new computer too (almost decided on tat one too) and then that isn't real issue either, but still it could be an option. Or don't you do that occasionally?
That's why I keep my D300 too - images that don't require the enormous resolution of the D880, they will be taken with the D300 for a while, also because I won't buy the whole range of lenses in one go. I start with the 16-35mm VR to be able to make the kind of images I made/do the type of shots as done in Berlin (see link above) on full frame - and over time (next month?) extend that with a 24-70mm.
Of course things may very well get faster than foreseen now. The idea I get from you is that once you start to use the D800 the D300 is quickly forgotten.