What ruined it for me was that EVERY quest in the guilds were urgent. 'You must deliever the corn at once, or all of Tamriel will fall.' I could not relax and do radiant quests knowing I had to go to a dungeon or an NPC was waiting for me.
Exactly. I've only done the Thieves' Guild and College questlines, and both times felt rushed through. Part of that is simply because it was my first playthrough and I wanted to see how it all shook out. But the radiant quests certainly seemed to pale in importance with the main questlines, especially when you have a clearly important NPC tasking you with the fate of the world.
In future playthroughs, I can see myself actually just doing the radiant quests indefinitely (that is, if they're repeatable?) rather than climbing the guild ladder. Especially the Thieves' Guild - I'd rather be a dirtbag thief than the epic leader.
From the sound of the College radiant quests, though, I can't imagine spending much time on those... Not a big fan of the College actually, which is too bad since it sounded cooler than Oblivion's MG. But you get there and I dunno, it sort of feels like Harry Potter. That was part of the reason I didn't do anything but the main stuff; my character is a badass legion mage, not some little student!