upsides

*He sleeps with his eyes open as is the way of the Elves, which isn't really a downside but it's a little creepy.
*He can be stubborn (i.e. refusing to be blindfolded in Lórien).
*No way can you keep up with him if he picks up the pace.
*He doesn't mind Elf-caves, but he'd pay gold to be let out of the caves of Dwarves - if he got lost in them (they are not as light as Elf-caves, and much deeper).
*The nicknames he bestows on people aren't exactly flattering. (i.e. calling Merry 'Master Sluggard').
*You can't hear him sneak up on you, lightfooted Elf that he is.

*He's not bothered by raging snowstorms.
*He can run on snow.
*He can tell a sparrow from a finch a league off.
*He recycles (i.e. his arrows).
*He can build boats.
*He sings.
*He climbs trees.
*He can fight with knives.
*He loves nature.
*He readies an arrow on a bow faster than the eye can follow.
*He's very good at standing watch.
*He knows how to navigate fast rivers. *He's got a killer aim.
*He rides horses bareback.
*He's royalty.
*He has a way with good animals.
*He's not afraid of the Dead of Men.
*He's gorgeous. (written by J.R.R. Tolkien, confirmed by P. Jackson)

"Lesser" Upsides:

Upsides