i bought the sp2 in early december with the intention of getting the power cover asap. i'm coming from a thinkpad and am used to 10+ hours of battery life. i figured a sp2 with a power cover would give me about that and weight is not a concern. At the store they told me the power cover would arrive in january. if you've used the sp2 without a keyboard you know it is very, very limited... definitely not good enough for daily use. so here we are three weeks into january and nothing. on the plus side, my thinkpad still works like a champ.
I just wish they'd release the thing! I use mine for lecture power points and mark-up note taking. It barely lasts a three hour class, and if it's not fresh off the charger, it won't make it. It's an SP1, so I think the battery life is slightly improved on the 2, but I'm skipping this generation and getting the next. Meanwhile, the power cover should give me enough power to get through class and a study session or two on a charge.