Over the course of the last few months I've preordered and cancelled all 3 versions at Amazon (WiFi, 3G, 3G Bundle). The bundle is just too pricey (and isn't really discounted much if at all vs. buying the items separately) and my memories of being a launch day 3DS owner are still too fresh.
Only reason for me to buy a launch day Vita would be to lock in the best chances of getting a version that can be modded in the future to play my PSP UMDs, but in that case I'd need the biggest storage card I can afford so I'll probably go with the WiFi model since I can't really see myself playing enough in situations where I won't have WiFi access.
Only reason I can really see to get the 3G model is that they'll probably end up cancelling it within a year based on poor sales so it might be fun to have one for the uniqueness factor. I just can't imagine there are very many people that will want to pay a $50 premium plus a monthly fee that will likely average out to more than $100/year for crippled Internet access from AT&T that is only rarely needed. I think it was an interesting idea to include a 3G version of the Vita as an experiment, but I think that part of the Vita experiment will not be a success. On the positive side, they can just stop selling that model anytime w/o negatively impacting the market...unlike Nintendo's debacle with the 3DS that has 3D that most people don't like too much and certainly didn't want to pay extra for it (forcing Nintendo to drop the price down closer to DSi levels).
So at this point I probably won't be getting a launch day Vita, but I may pick up a WiFi version post-launch if they start coming out with some WiFi bundle deals. When I do get one, I'll probably be picking up at least a 16GB storage card, or possibly the 32GB card since that's something I expect to be useful for several years in all future Vitas (unlike the limited lifetime of those stupid UMDs). I'm definitely interested in the Uncharted and Resistance games for the Vita, so those will probably be my first game purchases.