You dont need a surface pro or anything like that just for sprite work. Pick up a Motion Computing Le1700 for 150 bucks or whatever from ebay and put gimp on it. it has wacom digitizer and it still used today by many many artists.

True, was just listing options you can buy NEW today....

As soon as you are looking at used and refurbished hardware, you might be able to pick up something useful for less.

Personally I am not to fond of older mobile tablets with digitizer layers or laptop/tablet hybrids. My Samsung Series 7 slate is one of the most powerful from the Win 7 generation, and its still just usable.

Can I make it work if I have to? Yes, of course, I use it on trips and in holidays for concept sketching and it does the job fine. Would I want to use it to create actual production ready work on it? God no, even with the pen stabilizer in Manga Studio the thing is just inaccurate and laggy. I always end up opening my files on my main workstation and retouch things, IF it is anything more than a rough concept.

Now, as has been said before, this will of course depend on what you need and expect, and how you work. Personally I draw with rather quick strokes, so any kind of lag will quickly end up in inaccurate strokes I need to redo. I can force myself to draw with slower strokes, but that feels unnatural to me. I guess depending on how you draw, the Series 7 slate could also be seen as a brilliant piece of hardware. It has the second latest generation wacom digitizer, and has rather beefy hardware, and an acceptable battery life... and a good screen to boot. Of course you will not find a used one for 150$, not yet....

Oh, and don't forget older Windows hardware has horrible palm rejection (or none)... you end up having to deactivate touch. Which isn't a big problem per se, its just that entering anything on virtual keyboards with the pen is.... painful. But that comes from someone that also hates touchscreen devices in general.