Well, I'm a 'one-shot' kinda guy, so I loose the desire quickly after my orgasm. Also, for me, it just doesn't work the same way after I've 'finished' first.
So, what's it like? Well, it's not really about the taste or smell, although I did learn to associate those things with cleaning up, and now it does enhance it. For me, it's about what it represents. My wife has just had sex with another man, and he finished inside her. If I'm present (the best way to clean up of course), then I've also seen the act take place, so cleaning up is a way of extending that experience. It's not something that I can really describe, or at least it justice.
Oh, one more thing about cleanup that I didn't see mentioned, 'eating cum is gay'. I'm not saying that of course, but a lot of guys will or do say that. A lot of people may also so that cuckolds are bi-sexual, or at least have that tendancy. To all this, I say hog-wash. Forget the labels, and do whatever it is that you want to do. Don't let other people ruin your enjoyment of ANYTHING.