My problem with RTwP is that it doesn't really simulate the D&D experience. Aside from that, RTwP makes casting AoE spells pretty pointless because between the time you start casting your spell and the time the animation ends, your target has moved 60' away from his buddies and is smack dab in the middle of a bunch of friendlies. No thanks.
It's also annoying to realize how many opportunities I miss with RTwP. Everything is happening so fast and furious, that I forget about that spell, magic item, or ability that could have given me a sure victory instead of a TPK. Yes I know the pause option is there, but everything happening at the same time makes party and AoE management much more difficult. This is a strategic element in turn based play that I greatly enjoy.
A CRPG using the Pathfinder ruleset (Kingmaker) presented similar issues for me; I had to actually download a mod to give the game a proper turn based mode. And sure enough, the 'enhanced edition' re-release of the game shipped with an official turn based mode, by popular demand.