No reason a full W8 tablet cannot replace laptop – that is entire purpose of W8.
Do you want a 10” screen for everything you do?
I would urge you to hold off until later this year when some newer models come out – a 13” MS Surface Pro (or equivalent from Asus, Dell…) with the Haswell Intel CPU (for somewhat longer battery life).
Things are gonna’ pick up for the W8 tablets as W8.1 rolls out. Win RT may survive, but the Windows app store will determine its fate – something flashy needs to happen for this.
The Surface Pro is still overpriced. Compared to ipad iy is not, but MS just doesn’t have the luxury of overpricing that Apple enjoys.