Achievements are likened unto a Double Edged Sword. While they do extend the life of a title significantly and can add a little bit of extra challenge and even fun to said title, they do have a dark side. Some tasks, as you said are downright obnoxious in terms of tedium and difficulty. For me personally, I've not gotten the Impress Vidic and River Styx Achievements in Revelations and I'm STILL missing the conversationalist from the first game.
Long Story shot, Achievements can be fun to collect but also a HUGE drain on your patience.