Surface Pro benhmarks show it be as fast as any ultrabook. The Micron SSD delivers 400MB/s read speed, 200MB/s write, whereas iPad4 is typically in the 20-30MB/s range.
CNET says they say battery life will likely improve this summer with Intel's Haswell and additional enhancements MS will make.
That's encouraging. The Surface Pro I'll buy will be half as thick as the current model with 8 hours of useful battery life and a Thunderbolt port.