The myth that sex on E will spoil you for sober sex was promulgated, if not started, by Simon Reynolds in his book, Generation Ecstacy. (Despite this myth, the book is a 'must read' for anyone who enjoys the combination of E and dance music. It's a great history of the Acid House explosion, the orbital raves, the early clubs, hi-tech pirate radio, etc. Wild times!)
That said, naked intimacy with a loved on is wonderful, with or without E. But it's different on E and quite worthwhile. And even if erections can be elusive, my gf appreciates the chance to completely slurp me without gagging and the sensations of her doing so are INCREDIBLE, even if my penis is not outwardly showing its usual appreciation.
Bachus