I'm about to make the change from a desk-top to a lap-top as my primary device. I'll be keeping the old desk-top for photo processing, Quicken and other off-line tasks, but won't be going on-line with it any more. Its a Win XP box and doesn't have the capacity to go to a later version.
There are some pretty powerful lap-tops out there in the $250 range. I'd have to get MS Office along with it, but it will have a lot more OOMPH that my old box which cost almost $900 when I bought it.
I don't like touch-screens so won't be going for a tablet type. DW has an iPad and she has to clean the screen every few days to get rid of the fingermarks.