I have camped in old pop-ups for as long as I can remember, but I recently took the plunge and bought a new Viking. I was amazed at the differences in what I was used to (1971 Starcraft was my last, and newest camper before this one). I have several features that I haven't used, but I have only been camping in it 4 times (Been a busy year :-( ) I personally would avoid a slide out. I looked at some, thinking that the extra room would be nice, but if you camp where sites may be small, then the slide out might not be practical. (I went sans-slide out and I am perfectly happy, and have friends who gripe about having to fit their camper in so the slide out will extend). I have a toilet in the camper, which is nice for those late night nature calls, but we only use it for liquid relief, if you know what I mean. DO look for good insulation. I have camped in below freezing temperatures in mine (well insulated bunks, roof and walls with blanketed tent material) and it is amazing that you CAN ACTUALLY KEEP A POP UP CAMPER WARM!!! In fact, the little propane furnace (another good investment) will run you out of the camper if you leave it on too high.
I know I am rambling, but as far as features, it really depends on how you will use the camper. I use mine MOSTLY in sites with water and electrical hookups, but occasionally I will go off the beaten path to an unestablished location. Your use may vary, but just think of this... you have camped in a tent for a long time, so you are used to a low level of "luxury" I suppose. Don't get too carried away, or you may lose the whole "camping" experience. Good luck!
