I've only just discovered the STCC servers within the last three days, and I bloody love it.
Having fallen back into LFS after a brief stay in TDUland, I randomly jumped onto an STCC server and was hooked straight away. The level of racing is bang on for what I'm after, and I've noticed my driving skill has risen already.
Managed to get my Bronze in two nights, and was quite happy about it. I went from being a backmarker on the UF1 server, to running with the front of the pack.
But, I don't think it should be forced upon people. It's not for everyone. But I would, and already have, recommend it to friends as a good way to hone their skills and have a cracking racing experience while they do. Even my "Pfft, gimme a BF1!" mate is hooked now.