For me, its the swinginess of high level play....
He who gets surprise round just plain wins...At the lower levels, getting surprised sucks but the AC/defenses and the HP of the target tend to insure that many creatures in the level 5-12 range can survive a couple of round plus a surprise round.
At level 13+ though, I simply suck as a DM I think since without fail, the chances of cakewalks and TPKs simply oscillate. There's just no middle ground I've found.
He who gets surprise round just plain wins...At the lower levels, getting surprised sucks but the AC/defenses and the HP of the target tend to insure that many creatures in the level 5-12 range can survive a couple of round plus a surprise round.
At level 13+ though, I simply suck as a DM I think since without fail, the chances of cakewalks and TPKs simply oscillate. There's just no middle ground I've found.