I have no problems with random encounters, particularly if I can choose whether to fight or not. Maybe well defined areas where powerful enemies respawn are more efficient to grind, though. Fallout 2 and Temple of Elemental Evil use random encounters, Planescape: Torment has dungeons with respawning monters, plus peaceful monsters and thugs that respawn in the streets and that can be taunted. I like them all. Morrowind has enemies respawning indoors and outdoors, and intellingent ones can be calmed too for a while with magic to talk with them. In Morrowind case the only problems are lots of crap in the loot and difficulties in selling the best loot, as most traders have little cash.