I have never traded oil futures, but from watching them on my IB account I would much rather trade IPE than NYMEX. With IPE the price levels mean something and there is much more electronic trade. With NYMEX all you doing is lining up to give away your scalp.
Quote from Chriz:
Yeah, this sucks. Its impossible to trade seasonal spreads with IB.
It's impossible to trade them anywhere. NYMEX only lists the spot month, adding the next month out at 10 days before the end of trading in the front month.