The removal of Aero was due to the fact it doesn't fit with the metro design, as it is not digitally authentic.
Having said that, I actually find the removal of Aero on the windows to be more cleaner than in 7. The transparent Taskbar kind of keeps that vestige there, although I really like the transparency on the Taskbar, it looks more digitally authentic; no fake rendering or lighting effects. Just transparency. The Desktop that remains looks more like the Longhorn concept than anything. Especially when you have white windows, the feeling of content first over UI first shines. Since I use white windows, I've noticed I don't even glance at the window chrome until I need to close it, as I just manipulate the windows with my Touch Mouse. Theoritcally, white window chrome was supposed to be default along with a light blue Taskbar, but Microsoft went back on that.
I find that a non-Aero Desktop could had been better designed. Using the Office 2013 apps, they could had used that as a design template: move color down to the bottom of the window and have a 1 pixel color outline of the window. Office 2013 looks SO fresh and modern and metro that it's almost a shame that the design wasn't used in Windows. I also think they should had focused on system wide personalization, so a color set would be predominate on both Desktop and Start Screen and possibly for the apps as well. I'm also not OK with the Aero iconography on the Desktop when Office doesn't anymore and nothing else on the UI except for Desktop does. I'm also not too impressed with flattening down some Aero animtions like the loading bar animation. I don't get it, there is a new spinning ball animation and a horizontal loading metro animation but yet those aren't in the Desktop. Overall, if they did TRULY metrofy the Desktop, I bet the complaints of the overall UI that it doesn't feel right would be dissipated.
I'd be ok with transparency as long as it is consistent across the UI. Like for example, transparent colored tiles on a solid background type of thing.
But overall, I'm fine with it, not peeing my pants over it. Although it might take a bit for some people to get used to. I recently installed the RTM on a friend's puter that had the RP, and they noticed there was no Aero on the windows. They were a bit disappointed by that, but they got over it and doesn't seem to be a big deal now.