I will only say this, people, most of them from forums like this one and Most reviewers (until S6 Note 5 and S7's TouchWiz versions) had always mentioned TouchWiz as a Con, well, after more than 12 flagship phones in the last 3 years, from most Android OEMs like Sony, HTC, LG, One Plus, Motorola and Samsung, I've always appreciated what TouchWiz has brought to the Android world, basically I've preferred it to all other skins and a lot more than Vanilla Android. It seems that finally Google gave up and since latest Android versions and soon N, is incorporating things that Samsung has developed and incorporated into TouchWiz for years now.
I just got the HTC 10 on Saturday, traded the S7 with the Jump on Demand and kept the S7 edge (best phone I've had in my life) and I'm testing it since then so it's been my daily driver since Saturday and boy... People talk trash about TW and praise Sense and first thing they say is that is a Pro when compare it to any Galaxy phone, wow, in simple words, I hated M7's Sense and I simply hate this version even more, first thing I did after a couple of hours trying was to install Nova, a launcher that I stopped using since I got the S6 and it's themes.
HTC themes are a joke, really can't say which is uglier, default UI or all themes I tried. Basically vanilla Android quick toggles and Settings menu, so from people that comes from TouchWiz that's simply lacking and boring. Icons are horrible for me and the weather widget... Samsung one put it to shame. For last, that app drawer scrolling vertically, mehhhh.
If it wasn't for Nova I'd return it already, so with Nova it's a keeper as its a very good phone with a solid build, still not the best for me, S7 edge is the clear winner in all areas that matters to me plus the extra unique Samsung features such as Samsung Pay and Quick Connect, and the extra things that are not on HTC 10 like the Multi windows, wireless charger and water resistant. Only thing I like more on the HTC 10 is that it's not a fingerprint magnet, not a deal breaker for me, but very nice on the HTC.
But talking about UI for now, I must honestly say that you don't know how good and convenient Touch Wiz is as a whole until you try something else and begin missing the unique Samsung features.