I've only used the Kadee HO couplers where I needed them a special application, like an offset shank on my SouthWind 2-8-0's:
and on any "vintage" cars I bought that already had them installed. Otherwise, the HO couplers look too small to my eyes.
The distance between freight cars using 802's is about 3 scale feet, which is about what it is on the prototype, so I really don't see an issue there, but to each his own.
I can see where cost can be an issue, but as I usually buy a package of 802's when I buy a locomotive or car, that difference is blunted somewhat. Plus every "scale" locomotive I've bought directly from AM, they've thrown in a package of 802's. They even installed them on my last purchase: UP E8's...
The irony is I'll have to de-install them for body mounting and fill the pilot gaps with a modified insert, a project currently on a very crowded back burner.