I'll admit to being one of the naysayers on Revere and thus far, I am quite happy to be wrong. I'm not, however, convinced in him just yet.
1) To answer the original question, I doubt anyone would say that the arm is more important than the range. I'd agree that range is the most important defensive aspect of OF because it eliminates base runners alltogether. The arm, however, does cost the Twins runs. The question is how many runs are picked up with range that are cost with the arm. If I were a guessing man, it's probably 3 to 1 or so, which is still a net win... that said...
2) Revere's biggest problem is a lack of power. That hasn't changed. I don't know where people get the idea that a SB is the same as a double. It isn't. It is certainly better than a single and nothing, but a double will clear the bases with just about any runner on 1st. A stolen base does not advance runners, and last I checked, we have a manager that talks the talk with SBs but doesn't call them nearly as often as he should. This just means that Revere at the plate with runners on will typically generate less runs than a Mauer, Morneau, Willingham, or Plouff in the same situation. Putting him up at the top helps limit that exposure, which is fine.
3) His other problem, that to date he has fixed, is his ability to get on base. I'm not convinced that major leaguers will not adjust to him a bit, but based on what I saw of him this week, the kid should be able to consistently hit around the .300 mark as long as he takes good at bats like he did this series and continues to make good solid contact on the ball.
4) Like his pitch to contact brethern on the mound, Revere's skillset walks a very, very, very fine line. His usefullness will be non-existent when the speed drops off should he not develop any power. A small tweak to the hammy or something like that will result in an entire lost season. This is not the type of guy you want to depend on.
That said, his ceiling is still a Jason Tyner type player with better defense. It's a nice stop gap, but it isn't a stand out guy either. Tyner didn't walk much and could hit for average. He had no power and played pretty decent defense. I can live with a guy like that in the OF as a stop gap, but in reality he's more or less a very very very good 4th OF. Given that the Twins are not in contention, this should make it easy to trade Span if they want to add some starting pitching, as Revere should be able to hold down a spot until Arcia, Hicks, and Benson arrive, but to count on him for more than that is not a good idea.