What we've observed is that removing player levels from the game cause players to stop referring to levels in the game. We're still waiting to gather enough data to determine if this has had any affect on player quit-out rates or not.
Seeing as how in Ghost Recon Online, compared to other titles, levels are not really that important. Most of my Assault's gear is level 1-15 (keep in mind there is no stat improvement for levels, they only control unlocked gear) and I have no problem holding my own in a game. My Spec is in level 1-7 gear and he holds the record for my longest streak. The higher level unlocks, with few exceptions, primarily provide weapon variety, and are not necessarily static upgrades to lower level weapons. Yes, there are powerful high level weapons, but I can't think of any of them across all classes that flat-out out-class their lower level counterparts. The devs have done a good job of balancing all weapons, and the changes in fire rate, damage, recoil, etc. are usually offset by changes in an opposite area. For example, more damage usually translates into a lower fire rate and higher recoil. This is true of every weapon that comes to mind right now, but I could be overlooking something.
I digress, it's safe to assume that level has very little to do with power. A level 1 can melt face and top a round full of high-levels in the hands of an experienced player. That, in my opinion, says a lot about Ghost Recon Online. If I really had to put a power add to higher levels, it would be that players level 9+ have an advantage over players 8 and under in that they have 3+ insert armors and team abilities available to them.
In my opinion each classes best weapons are in the level 1 and level 5 brackets, and the rest just provide niche play style customization, and aren't necessarily "better" for every player.
I think I've stressed my opinion enough :P