Tablets make you work and especially sketch much faster but that's about it when it comes to pixel art.
Of course getting somewhere fast can be a motivation to keep it up instead of losing interest -I would know- but if you're used to the pace of a mouse, the results will be the same.
Once you're in the refining stage and deal with individual pixels, the speed advantage of tablets pretty much evaporates.
You will only get results you could never get with a mouse when doing normal cg art on a tablet.
That's where they truly shine.
Don't be fooled though, a tablet needs some time to even get used to and in the end of the day, the tools don't matter as much as what you do with them.