I think there are so many factors affecting the enjoyment of the game that it's hard to get a clear picture about how one particular aspect affects gameplay when they're all muddied up together.
The 128 players does create some ridiculously chaotic situtions where whether you live or die is almost randomised at times. It's makes for a very frustrating experience with very short lives and respawning continuously.
There just seeems to be a lack of any kind of flow, makes it very hard to play intelligently. I think it's made worse by wingsuits and grapple hooks - opposing players can literally pop up anywhere.
Performance is part of the issue too. When things get hectic, frame rates drop and things get less fluid, downright unplayable at times.
There's a lot of balance issues too obviously - like that stupid little tank thing. How that's allowed in the game is beyond me.
The terrible sound design doesn't help either, it gives you so much less situational awareneess then you had in previous games.
The controller settings (at least on xbox) feel off and unnatural no matter how much I've fiddled with them.
So with all these issues thrown in together, it's hard to get a clear picture of whether or not 128 players is a fundamentally bad idea. I think that will only become clear when the game matures and a these other factors are taken out of the picture.
As it stands, it affects the way I play a lot - I find myself much more inclined to stand off from situations with a DMR than to pilee into the chaos.
Maybe in time with the amount of resources they seem to be throwing at the game, it'll improve. Hard to say though. Especially when they're clearly committed to some design decisions which I just don't like - specialists etc.