So I have this vise, and the jaws are kind of rough. Is it okay to weld on them and then grind them down smooth, or is this a bad idea?  If thee is a better way to repair the jaws, I would love some feed back. 

Following; I have a similar issue with my vise (currently using a couple of pieces of angle iron as jaw liners, but would be interested in a more permanent repair).

I wonder if it's cast. I would think anything forged would just dent or mushroom. I dont know, just thinkin out load. Maybe do a spark test or clean up an area and do a spot weld to see how it reacts. I have a vise thats had an extensive repair done to it and welds look good. The area marked with chaulk is the weld on the reinforcement straps.

Spark test on the jaw area as many had a High C face layer welded to the wrought iron body.  If so I'd repair it using standard anvil repair techniques.

If it was mine and bugging me so much I couldn't stand it (and that'd be a high bar to meet), I'd TIG weld filler with stainless rod, a bit at a time, cooling between those bits.  Stainless won't tend to pick up carbon like other rods will so is more forgiving.  Since that's not really structural and only fill, you should be able to get a good result without really affecting the jaws much. Finish file the patch.

Stainless also tends to be pretty ductile so makes a decent jaw face for something which doesn't need hard jaws.

Obviously YMMV

The vise I have set up currently has that issue as well. It isn't a problem for what I do yet so it will have to wait for a makeover until I get my new workbench built and my other vise mounted. 

Hmm have a vise with one side of the jaws soft and the other side hard could be useful

I think I will probably let someone that is a better welder than I am do the tig weld on it. Until then I will start working with another vise or insert the angle iron jaw liners as mentioned by JHCC. Thanks for all the input.