We used a 3 part system in the first tub-shower enclosure from Laticrete, but that is a messy process. It kicks off relatively quickly, and is more like cleaning up grease or butter than normal grout. It is really maintenance free, but there is a new system out called Grout Boost.
Use normal sanded or unsanded grouts, and add Grout boost in place of water. It does not kick off like laticrete, is easier to clean up.
The only caveat is, don't leave standing water on it for the first ten days. Some folks will start showering in a couple of days and just wipe it down with the bath towel.
The nice part about grout boost is the color choices, you can pick from any grout company and just add the boost. Laticrete has a limited color choice by comparison.