I've found the dust cover to be very useful to keep dust and debris out. Use mine constantly in the field and when transporting in an open vehicle on dusty roads. Have no interest in an AR upper that lacks a dust cover. Wish some of my other non-ARs had dust covers.

As for the forward assist, I've only used it on one AR15, a real old reverse engineered beater that I got dirt cheap and spent the next year ironing out most of the bugs. No wonder it was a super bargain. Had to machine some parts out of spec to get them to work. The use of the forward assist, btw, had nothing to do with a round that would not chamber. The problem was the bolt did not go into battery on an empty chamber. Something, maybe debris, hung it up to the point where the action could not be opened. The forward assist was very useful in getting the action open by unjamming the bolt.

I prefer to have a forward assist, even though chances are I'll never need to use one on a quality AR. I view it as a dire emergency option and don't mind paying extra for it.