Honestly Scholo/Strath were much more fun in the intended 5-man difficulty than they were as the 10/15 man zergfests that people ran them as. Also eventually they were fixed so that you couldn't do that any more IIRC. It's been several years.
LFD is pretty much the best thing ever. Before LFD if you wanted to run something off peak hours you had to spam for like an hour to find people ... and if you were DPS, GOOD LUCK. Then once everyone actually got to the instance about 50% of the time someone would decide they didn't really want to run the instance and bail. Then it was back to spamming. OH BOY SO FUN!
LFR is great too. Kind of sucks for the hardcore raiders for the first tier of the expansion, but going forward it should have very little appeal to them and lots of appeal for the casual players. Good stuff all around.
My only complaint is that the LFD tool killed off any sense of community in the game, but I think it was worth it.