So, my opinion on the new HUD: It's nice, it looks sleek, it fits in with the graphical direction they've been going since they updated SR. I like the new features, such as being able to see your teammate's summoner spell timers, and a decent timer on teammate's ultimates instead of just being a green or black dot. I also like the fact enemy death times show up next to your team's icons now.
This said, the new HUD is WAY too compact in areas it didn't need to be. The dots under the spell icons are way too small (not a big deal until you're playing Kha'zix and are asking yourself "Did that point in my ultimate place?" Accidentally evolved ultimate at lvl 6 because of this), the new stat info for your enemies is way too small, the stat info for you is just... stupid. You have to hold C to see your armor and MR. Teammate's hp bars and mana bars are WAY too small, and in an awkward position now (might not be the case if they were bigger)
Most of my complaints can be dealt with over time of using it and memorizing what icons line up to what stat (and most of them are pretty simple to figure out), but I, like most people that posted, liked being able to see the giant letters and numbers saying "Cooldown reduction: 20%" instead of having to find a tiny hourglass to see a tiny 20% that takes longer to actually read than the other.
The other complaint I have is that in the character info screen, it kept your sight to the middle of the screen which is where most of the action happens. This new one has you looking down on the lower left hand side of the screen where NOTHING ELSE is at now.
What I propose is making it more customizable, being able to move icons around, make certain windows bigger or smaller, and other miscellaneous customization features as opposed to changing it back to the old HUD like people are requesting. I would also propose that your character stat window is a permanent thing in the lower left hand, or at least be able to toggle it with C instead of having to hold C. As I said, I like the new features of the HUD, but it's just needlessly compact, and customization features like I suggested would fix this.