I've seen the MotoGP live several times in the UK at Silverstone and earlier at Donington Park and as you say, those bikes are loud! The sound on TV doesn't do it justice.
I normally make a weekend of it, wander around the whole track on the Friday and Saturday taking photos and checking out the memorabilia before sitting in a grandstand on race day.
I watched the COTA races live on TV and man, were those Moto3 riders that had that huge crash on the back straight lucky to all walk away from that!!!