if you don't use it, you need to gage productivity in some other way. one way this is done is to agree in advance on a price for a certain agreed upon amount of work. but that isn't going to work (at least straightfowardly) for a startup that wants to work in an open-ended, semi-unstructured way.

you can also ignore it. if everyone seems to be working very hard, then that's probably ok. but if some people seem to be working more than others, then it can start causing problems.