I know it's "not PayPal", but if you just have need to use an alternate online payment provider, I've been told some
e-liquid suppliers now accept
Dwolla, which does not have an ecig ban.
Try hitting up Andrew (NCVaper here) from
Joogler Juice - I know he was taking that at one point.
He's got all your other requirements (reliably fast, dirt cheap prices [no joke], and also has 510's), so I figure it's worth a shot for you.