The first is the recent apps interface. The HTC has a dedicated "Recent apps" software button, as do all recent Android devices, but it then displays the apps in a horizontal full length preview and only shows you one app in the center of the screen at any one time. This means that you have to actually scroll/swipe if you want to switch to anything other than the last app you were using and that you have no idea how far along the list you will have to go until you actually land on the app that you were after. You may as well go to the home screen and re-open the app directly. Kinda broken.
The next is the contacts interface. Upon opening the list you are not presented with a list which has the default android "quick view" (my way of describing the ability to click on any contact image for an overview of their information and ways in which you may like to interact with them), instead you just have a long list of contacts where you need to fully open up their contact card to see what you "know" about them. Not a big deal but still a small step back from the simple and intuitive access in vanilla Android.
The other part of the contacts which took me second to adjust to was the way in which you control which contacts you actually see. By clicking on the "People" label at the top, you have to wait a second for some weird reason while it loads your contact sources, and then you can open/expand each of them to select which "groups" you would like to see. The only reason I raise this is that I see this as more of a settings option than a primary interface option, so it did take me a while to find. Again, not a big deal, but a creep away from them beings "settings" and back into user land display. This may also be considered a nice easy way to access this display control feature, but seriously now, how often to you change that "setting"?
My last gripe is, again possibly minor, but in my opinion another break in the user experience, where I continually found the "menu" (the three little dots for the context sensitive options/menu/settings access) to be at the top of the screen, whereas the default Android system applications place this at the bottom to the right of the main navigation software buttons. Just means that you have to shift your hand/finger to the top of the screen, a little harder than tapping the bottom right when operating with one hand or two for that matter.
I guess my point in all of this is that Google has spent countless hours in research, statistical analysis and user interface and experience design to come up with and be where they are now with Android core. Now it just seems to me that with all that in mind, you would need a very, very, very, very good reason to make a change to that and if you did you would want to make damn sure that is actually improved every aspect of the UI you were touching.
I say NO to all manufacturer skins. I have yet to see one that actually improves on the entire system. Sure if you want to replace the camera app with something smarter (although with 4.2.1 that will be a hard task) or a better dialer (again, getting harder and harder) or any other app for that matter, consider what you are undertaking and consider why...cause I am not sold on any of them yet and have seen and used quite a few.
The other big point is that these "skins" delay handsets from receiving recent releases from the Android project and add to the argument of fragmentation of Android. Nexus and Google Experience Devices (GED) all the way!
/end rant
