In some forums dedicated to the Surface line, the concensus seems to be that unless the battery life is a big issue and you need a bit more hump, that the Surface Pro 1st gen is deal to get. For me, the 1st gen is on par with my MacBook Pro w/Retina in performance, screen quality and battery life, though I think the MBP may have a slight edge in battery life.
In those forums, many of those looking for the SP2 are looking because they want the 8Gb version with a bit bigger SSD. Most of them are using them as much as a desktop replacement with some relatively minor on the road useage.
The SP1 with 128Gb SSD has about 90Gb of free space after it gets the first 69 updates to Win8 you have to do in order to upgrade to Win8.1. And most Metro/Modern UI apps don't use much storage space at all. Desktop apps vary wildly in space needs. The default config on the SP's is to save to SkyDrive, though not everything actually pays attention to that, in general just the MS apps you get.
On mine, I even set up Hyper-V (virtualization), installed Ubuntu on it to run virtualized, and still had plenty of pep.