I didn't really want to go into detail because it's quite circumstantial. There's three possible issues that I know of.
1. Maps aren't designed for the new physics
If the maps happen to become less fun to play, it will make the game worse until the maps are fixed, or new maps are made. We've got a buttload of maps though, so there has to be some maps that would work well, or even better with the changes. I hope the map committee can sort this one out.
It's not like I'm drastically changing the way the physics work. Jump height, velocity, acceleration, etc. are all the same. The differences are in the little nuances, like not stepping onto a ledge when you should.
2. More variables and more unpredictable gameplay
New alterations to the physics, such as sky gliding will increase the amount of techniques one can use. This becomes a problem for people who don't like to keep track of even more things. With this update, you could glide for unrealistic amounts of time by a random release of the jump key, and jump from ramps in two different ways, making the gameplay more inconsistent and unpredictable. One could argue that this is a good thing, sure, but it depends on how much more unpredictable the game becomes. Everyone has a threshold.
Hopefully, that's a good thing. I know a lot of players are getting tired of the same-old same-old. Discovering new tricks and paths in old maps might liven things up a bit.
3. Realism
Skygliding looks more unrealistic than bumping into the sky does (because it can't be reasoned as easily, if at all), so people might be put off by seeing people float around on top of already flying around.
The physics are pretty far from realistic to begin with, so I'm not too worried about realism concerns, but, personally, I think floating along the sky is more realistic than hitting your head and dropping down. Ideally, maps shouldn't have sky brushes so low that players can run into them, anyway.
I'm leaning towards removing all of the major gameplay changes and just adding the bugfixes in the next build.
The changes
are basically all bug fixes. Some of them just happen to have more significant changes in the movement than others. For example, fixing the stepping bug (where you come to an abrupt stop jumping up stairs) made it easier to double jump on some objects and do ladder jumps.
What bothers me is that you don't lose control if you know what you are doing.
So you've never had situations where you're moving up a slope and somebody starts shooting a stream of paint so you need to stop or change direction to avoid it but can't because you're stuck "flying" up the slope? It's true that you can master the navigation of every map with enough time, but sometimes you need to change tactics on the fly, plus not everybody has the time necessary to master all of these little nuances.
Thanks for the feedback. Feel free to post more concerns.