Okay, so first of all let me explain that I am NOT a pro TT player, I am writing this as a casual TT player who actually rather enjoyed the older map even with it's many flaws.
Now, with that said here are my opinions on this new map:
I love, yet I hate it.
I love the map, I love the music, the effects, the detail, I love the work and effort that Riot has put into it. It is fast paced and teamwork has such a huge impact on the game and proper coordination between the three players will make your team nearly unstoppable.
I love the sounds from capturing the alters, the things they say when you cap them. I love Vilemaw, he actually feels like a bossfight and is very cool to both kill and dance with.
I love that you normalized the jungle and fixed both the broken turtle tactics and the flashing over the wall to snipe the nexus.
Now what I hate:
It honestly doesn't feel the same as the old TT. As many others have said, it kinda feels like a TT/Dominion hybrid, and I do love dominion, but I feel like it takes away from what the old TT played like. The bonus starting gold also adds to that feeling, while nice to have more items, it just doesn't make much sense to have that extra starting gold.
I hate how small the map feels, the removal of the upper jungle makes the map just seem so tiny... it takes no time at all to move around the map,especially with the speed shrine, and that adds to the dominion feel. In fact, this is my largest complaint about the map, the normalized jungle is nice, but it just seems so tiny, even though the number of camps are the same (excluding red, but I'll get into that later). There is less places to juke, less places to run and kite, it almost seems to take away from the strategy, but that is just my opinion.
Now, more on the jungle: I hate the lack of neutral buffs. One of the things I loved most about TT was the variety of buffs it had. You took all those away, controlling red was a key part of the old map and having those jungle buffs made jungling feel better (well, when the camp spawned that is :p). I realized that with the normalized jungle maybe having consistent buffs was a problem, but still, not a huge fan.
LACK OF WARDS. Second biggest complaint and this really irks me. Lack of wards is just annoying, it gives so much power to champions who can get vision on the brushes without entering them (like Orianna) and Teemo with his goddam shrooms (the map control teemo gets is just broken, to be honest). I realize that with the smaller map wards would be a bit too strong, but it's just annoying. It makes the gamemode feel less and less like classic, and even more like dominion as all the things like buff control and wards really add to the strategy and feel of the old TT.
I am not saying the map is bad, it really is pretty good, it's just not Twisted Treeline.
EDIT: Adding more maybe getting Riot's attention.
I noticed they are adding it into the next patch, I don't think they should do this, it hasn't been in beta for too long and many players have strongly and eloquently stated why they don't believe that the new map should replace twisted treeline.
I honestly do not understand why Riot made this whole new map as opposed to just having the old TT, but with the fixes that were needed (nexus placement, wall width, jungle camps). While I appreciate the effort, time, and creativity expressed in the new map, I do not believe that it is ready for live, nor do I believe that players will embrace the new map.