Unfortunately I'm not going to be much help in your case. I only use my HTPC for things I can't do on my blu-ray player, like Cable TV in WMC, web browsing, BBC iPlayer, and miscellaneous video formats WMC can't easily handle (I didn't have much luck with Shark's codecs). So Netflix, Amazon, Pandora, etc. aren't on my PC. Besides, the Netflix PQ isn't very good on a PC compared to my player (720p vs. 1080p).
Anyway, I run the following profiles at the moment: Win 7, WMC, Chrome, Daum, iTunes, and Spotify. I tried Youtube leanback but it was horrible (the profile was fine, but the leanback site is awful). Same goes for Hulu Desktop, it's pretty worthless. And the fact that WMC only launches Hulu and that it won't work with extenders makes it even more worthless.
I added some extra buttons and macros to WMC, Win 7 and Daum. It was pretty easy using the editor in the app. The hard part is the research and testing for finding the right keyboard shortcuts. I think it would be easier to start with an existing profile. The Hippo site has really great documentation on creating profiles, so it looks very straightforward to me. While I haven't needed to use Dropbox syncing, it sounds pretty easy too.
I typically use the Pandora app on my blu-ray player, but on the PC I don't think there's anything you can do to change the web app.
One thing I did do that may be unusual is install the VNC app on my iPad and iPhone since it can share the same VNC server that Hippo uses. So not only do have keyboard, touchpad and profiles from Hippo, but full remote desktop capability when I need it.
Otherwise it looks like you're the trailblazer here. Please post back with your progress. And thanks for starting this thread.