We currently have a 28' C with 2 slide-outs and would not have it any other way. Before buying, for a number of years we rented a variety of Class Cs from 24 to 32 feet long, with and without slide-outs. Based on that experience we definitely wanted one with a slide-out.
A motorhome with slide-outs is effectively a non slide-out unit when the slides are in. So if the weather is bad, say snowing and below freezing we can keep the slides in to prevent icing on the slide awnings. We have had up to 2" of snow on the awnings without a problem, and when above freezing slid the slide-outs in then back out to dump the snow. The slide awnings prevent debris and water from being slid inside. When out, the slide awnings and double slide seals prevent any water from entering in the highest winds and torrential rains.
We don't slide out the slide-outs when in transit so there are no issues parking in parking lots, etc. We usually park well away from other vehicles and park in a number of spots. I have also crammed it in a few places but like our cars tend to avoid issues with other people opening their car doors.
When we are on the go we still will slide-out even for a 1 night stay. After leveling it takes just a couple more minutes to take a quick look outside to verify clearances, then slide them out. If we were really tired we could skip the slide-out step. We have taken some day trips and do not slide out the rear slide in that case. When drycamping we have the engine running while sliding out or in to not discharge the batteries.
Our rear slide-out blocks 2 of the lower drawers in the large wardrobe unit back there. We handle that by appropriate loading of items so that when on the go we do not need access to those items. Other than the 2 drawers everything is functional. Our storage space is never full so we could actually not use those 2 drawers if necessary.
I look at it as the floor space of a 32' MH (non-slide) in a 28' length.