I use PHD2 but I find it can oscillate as Kevin describes. (It has some features useful for slit guiding like a virtual slit graticule and guiding on a specific location but does not have a specific algorithm to deal with a split star image)
I know Astroart has a specific slit guiding algorithm, though I have not tried it.
I think Prism is quite popular among the French spectroscopists. For example Olivier Thizy uses it with scripts to automate his observing