ISDN isn't a good option. Only businesses use it. Even back in the day it wasn't really suited to households. Far too expensive back then, and today it is just plain unreasonable, price wise, for internet.
These days the only people that use it are small businesses (some) and many large corporations that still use
PRI (internally at least). And these days basically no-one uses it for internet. Small businesses use wireless internet or ADSL (maybe ISDN if they only need internet now and then) and large companies use Diginet.
I wouldn't recommend anyone getting their internet over ISDN, but there are a few niche markets where it makes sense.
Radio - plenty of use by these okes, for outside broadcasts - with one line you're guaranteed 128k, anywhere in the world.
Tele medicine - Again, the guaranteed speed is key. You don't want your surgeon 'losing the feed' while he's inside your gut.
Small businesses - The lines have a higher priority when it comes to repairs, than POTS lines, so you get more uptime.
More numbers - for just R 20/month extra each, you can get up to five numbers on your line. You'll need a (relatively) cheap TA.
Video conferencing - often uses 4 x BRI lines, giving 512k down and up. Unless you've got a good quality 4M ADSL line, you're not going to get 512k up. Again, this speed is guaranteed anywhere on earth - no shaping & no contention.
So while ISDN isn't commonly known to most residential users, it's still widely used in a lot of places, where it's the best choice for the job.
Hennie, I'm glad you came right. Otherwise I'd have suggested setting up your own pigeon-frying 200km WiFi link (probably multi hop) to your nearest town, and plugging into an ADSL line there.