Thanks, guys! I did a brief check yesterday and found some info on the wall liner. It wasn't very complete, though, and didn't explain why the liner was hung horizontally -- presumably it's in anticipation of someone actually papering over it and too much vertical background wouldn't be good. The article I read didn't address taping over the joins; I assume that this should be done, or perhaps the joins are just mudded.
I've scraped off the popcorn ceilings, have more to go and it'll take a while as I really hate working over my head. I've tried both wet and dry approaches, and have found the dry, though a bit messier, to be preferable overall as it results generally in fewer gounges in the drywall. I use a scraper tool that encloses a 4" razor-type blade, easily removable, at the end.
I tried this, both wet and dry, on the walls with limited success. My belt sander really is not suitable for vertical work and I gave up on that approach relatively quickly. I saw on one episode of Color Splash (HGTV) that they used a disc sander to smooth out walls and I might go in that direction, despite the relative mess.
This time around I did what I could to roughen the surface of the texture, then applied joint compound over top. Then I sanded it smooth once it had dried. Some areas were hard to reach and the joint compound didn't go on as smoothly, neither was the sanding as successful. If there hadn't been so many cabinets I might have been tempted to just tear out the old drywall and install new. There is the problem that I've never done anything like that before and know it only on principle. That tends to leave out too many crucial gaps in procedure. I'm just sick of breathing in plaster dust despite the mask, and finding white dust all over the house despite my best efforts to contain it.
In two previous rooms plus the hallway, I did a neutral-toned faux finish that looks really great. I'm preparing in another room to do Venetian plaster, again in a neutral sort of tone; colors will come with the accessories. The room I'm finishing will be much fresher and brighter, and I just applied the first coat of primer on the walls yesterday. The cabinets have been done for weeks.
It's a good thing for me that my Dad taught me not to be afraid of tools!