Yes, it does take longer. They're harder to cut, harder to shape, harder to crown, harder to level. I've done it a few times, but it is hard work. Although if it is done well, it'll last forever.
The frets need to be pre-curved to match the radius of the fret board, but not over-radiused as you would normally do for nickel silver frets. Stainless steel will spring back out of the slot if it's over-radiused, rather than wedge itself in place when hammered/pressed in.
You'll destroy most hand cutters if you try to cut stainless the normal way. Use a diamond cutoff wheel for a Dremel instead.
If you're intending to undercut the fret tangs (eg for a bound fretboard) you won't do it with a regular pair of tang cutters, so you'll have to use the diamond cutoff wheel and/or files, which is more fiddly.
Leveling and crowning will be easier with diamond coated tools too. Regular files work OK, but will take a lot longer and wear quicker.
The process of fretting with stainless is largely the same as nickel silver, just takes longer and is more effort.