I assume you're flying from Gatwick? They use both 777's and 767-200's on the LGW-EWR route, with a 767-400 on the Manchester.
Service is nothing special in economy - not the worst, not the best, nothing to complain about. They have seatback screens in all the 777's, but no 'on-demand' programming like US Airways.
EWR can be a good or bad gateway. I've never had problems on the outbound, but for the late PM return, the place is often very busy making conning from a domestic flight difficult. The rail link into downtown NYC has just opened apparently, but I haven't used it. The taxi ride isn't too far, but traffic can be busy in the afternoon.
By the way, having booked through Virgin shouldn't make any difference on the flight. Just one point - what''s the actual flight number? You could be on a Virgin a/c with a CO flight number or vice versa. I'd have thought, if you'd book through VS, you'd get a VS flight number even if travelling with CO.