There was having sex with Cordelia in his dream. Might not count, since he could have been thinking about Buffy.
I used to find it odd that Connor didn't make him that happy, but it makes sense (when you fanwank).
The first time he lost his soul in the afterglow, the other time, mid-orgasm. I first thought "okay, orgasm, then all the world's problems disapears and you can be happy, even just for a sec" but then I remembered how it worked in Suprise. Still, I think it applies.
To feel perfect happiness, you need to feel a complete lack of pain. It has nothing to do with how happy you are. I'm think that Angel felt more happy when he hel Connor in his arm than when he was with Buffy, but he was also more worried when he had Connor in his arms than when he was with Buffy, because he thought about how Connor could get hurt.
That's the theory I'm sticking with anyway.