i have modern and retro bikes, i find that retro works fantastically in my local area as the terrain is mostly flat so super powerful brakes aren't a necessity, also i rode rigid on the HONC and i seem to remember (and gmonster will back this up as we were riding together) overtaking alot of 5 inch trail bike riders with discs and 22t x 32t gears that were walking up the hills and we were overtaking them down the hills!! i found that funny!!
i expected to have them on the ups but to be trounced on the downs!! but i was mistaken and i'm happy about that!!
horses for courses i say, i love my bikes, modern or retro, full suss or rigid.
i do think however that people who are new to riding are sometimes brainwashed into buying things they don't need by the brands/mags/sales guy or whatever whether that be excess suspension, excess disc rotor size, excess overbuilt frames, or newer thoughts on wheel dimensions!! :?
you know somewhere there is someone with a 10 inch full suss with 250mm disc rotors with a 650 back wheel and a 29er front wheel that is also single speed (but with a mech hanger just incase coz they can't commit) with and eccentric b/b aswel as iscg mounts (just incase), not to mention a huge amount of hydroforming of the titanium frame with carbon inserts to make it lighter eventhough they want to ride it abusively!!
being 10inch travel aswel they'll expect it to climb like a banshee!! they will also be convinced by someone that tomac was right and it needs drop bars . . . . . of course all they will want to is nip to the pub on it!!