I have really enjoyed my SP2 as my throw-in-the bag device but it's aging. At this point, without the power assist from the powered keyboard (which pushes me over 3lbs), I am battery constrained to about 2.5 hours. That's ok for having a quick meeting or watching an 30 minute episode on Netflix but it doesn't leave much to spare. This speaks to the fragility of MS' approach with having a machine I cannot swap a battery out with... so that's a strike against MS and a strike for the SL 3-4 years from now too.
As it stands today, it seems like it's a significant improvement in battery life, power, same weight, huge screen upgrade and - for me now - a more desirable form factor. I just cannot see what's not to love about the SL.