I've done with an inkjet. As Al commented, to prevent smearing it was necessary prep the sheet with a light coat of the "fixer". After printing I always let the ink dry for several hours before spraying another light coat (or 2) of the fixer. I get my artwork either by making a high density, eg photographic quality, scan or typing in MS Word. Fonts are available for most lettering styles, eg Amarillo for USAF stuff.
I've found the decals would stand up to a fair amount off poking and prodding to get them into final position and reacted normally to setting solutions.
Just remember that you might have to double up to get the color density you want and white areas will need to be painted either before or after, or the whole thing printed on white decal sheet.
Very good results can be achieved, the most important part is the original art work.
Didn't mean to drone on, but I hope this helps, I'm pretty sure using a laser printer will require much the same techniques. I believe that using a laser jet requires decal stock, you won't get usable decals using inkjet decal paper in a laser printer.
P.S. I'm not the friend Al was talking about, I think it's guy that makes & sells very nice inkjet decals at model shows.
