I'm starting to think that the best titles to buy digitally are the ones that you want to just pop in at a moment's notice and play when friends are around. When I'm having to fiddle around with discs, I can sometimes feel my family or friend's attention waning.
And more importantly, it's soooo much easier to lug the console around to parties with just a portable HDD than with five or six discs.
But, it's gotta be titles I know I will keep forever and are less likely to lend out. So no on RPGS and single player adventure or puzzle games going digital and yes on party games, smash, kart, and probably 3d land. Nintendo Land fits into this category. But, I'll wait for another price drop.