Yes, I miss them loads. I ran one myself for about a year using MaxsBBS.
One thing I really miss is split screen chat where you see each character as the user types it, rather than having to wait for them to press return then a whole line appears. I know there are ways to do this now, but its not practical to get all your mates to install an SSH client when they already have msn/skype.
I don't miss the phone bills though. When I was 14 and I got my first modem my mum was not impressed at the 350 pound phone bill we got at the end of the month. I still remember when BT introduced 1p a minute weekend rate, it was amazing. midnight on Friday night I'd be straight on the modem, but all the BBS's would be engaged. The alternative was spending hours playing with the phone trying to find and get into PBX's, which I miss nostalgically but wouldn't want to waste all those hours pressing buttons again.
