Now we have Dragons but the difference between them and Oblivion Gates is that if you ignore a Dragon it's going to follow you and kill every NPC you go near potentially ruining quests, killing shop keepers, etc. After dropping a Dragon for the 30th time it gets really routine. Dragons arn't a challenge, just like Oblivion Gates weren't, they are just time consuming but as I pointed out earlier if you ignore them the game will punish you for it.
All of this would be a lot more bearable if the game wasn't literally throwing Dragons at you by the bucket load.
All in all I feel that the frequency of Dragons needs decreasing somewhat with their difficulty increasing.