I always take the exit row when avail (but then I'm 6'4"). Regardless of what row I'm in, I seem to have the unforunate luck of always getting the seat next to me filled, even when many other rows have empty middle seats

UA still blocks the empty middle seat adjacent to elites, and I more often than not end up with a seat-mate on full-flights, so having this feature is great only at time of booking and not in practice, IMHO.