Damn, I just posted about this in the 360 forum BEFORE I saw this thread.
I bought Lumines over the weekend while under the influence of both friends and alcohol. "LOOK AT THAT SHIT, buy it up man!"
However, overall I have been pretty restrained as far as buying crap I don't want. I know the day may come where the PS3 or Wii becomes more appealing to me, so putting money towards Marketplace points would basically become throwing money in the garbage. Less money I've spent on XBLA, less guilt if I decide to sell the system later.