Most underrated U2 song: non-single? If You Wear that Velvet Dress (mmmm) Single? Ground Beneath Her Feet. It took me several listens to really enjoy this one, but after that I was addicted. It's a very simple yet beautiful song.
Most overrated U2 song: I'd have to say "One" as well... or maybe "Still Haven't Found". Perhaps a better word for these songs would be "overplayed".
Most underrated U2 album: Pop. I love the whole tongue-in-cheek approach, and it sounds very different from the rest of what they've done. A lot of people don't appreciate that, but it takes courage to go out on a limb musically and say "to hell with album sales!"
Most overrated U2 album: All that you Can't... There are some real gems on the album but as a whole, it doesn't really tug at my heart (or my "dancing shoes")
First U2 song you ever heard: I think I might have heard UF on the radio when I was little, because it sounds very familiar and brings back hazy memories (I was 3). I think the first song I heard and recognized as U2 was Desire or With or Without You.
First U2 song you heard and loved: With or Without You. (yet I complain about One!)
All-time favourite U2 song: Mysterious Ways
All-time favourite U2 album: Achtung Baby, baby.
First U2 album you owned: Rattle & Hum.
U2 albums you haven't got (yet): The only "offical" U2 discs/vinyls I don't have are the elusive pre-Joshua Tree singles, one or two Rattle and Hum singles and a couple Zooropa singles.
Favourite U2 era: Achtung/Zoo or Elevation
Least favourite U2 era: I haven't a clue.