Software
The U11 still includes HTC's Sense skin atop Android 7.1, but the company has worked hard to improve Sense over the last few years, stripping out a lot of unnecessary crap in favour of stock Android elements. The end result is one of the better skins currently available, certainly better than Samsung or LG's offerings.
Many key areas of Sense are essentially stock Android. The notification pane, settings screen, and several stock apps are either directly from Google, or only minor modifications on what Google provides in the vanilla experience. The launcher is pretty similar too, aside from the app drawer, which uses HTC's Sense style.
Sense actually looks quite good these days from a design perspective. HTC has looked closely at what Google provides, and expanded that theme for their additions here. As a result, Sense almost looks like a natural extension of Android, and that's the mark of a great Android skin: one that melds in well with stock Android design elements, as of course some stock elements (and apps) are mandatory inclusions.
There are very few bloatware applications on the U11. Aside from HTC's Mail application duplicating functionality provided in Gmail, there are no other duplicate apps. HTC uses Google's Photo and Calendar apps for their respective functions. Even Google Play Music is utilized over a stock music app. HTC has chucked some unnecessary apps on the phone like Under Amour Record and News Republic, but these apps can be uninstalled so it's not a big deal.
HTC includes a Boost+ app on the U11, which we've seen before in Sense previously. Like many other Asian phones, this sort of app includes junk-clearing functions and "speed boosting" features, which vary in their usability. BlinkFeed is also included, which first debuted many years ago now as a decent news aggregator integrated into the home screen. Of course you can disable BlinkFeed if you don't want to use it.
There aren't many other outstanding features in Sense. Things like theming support and several battery saver features are now widespread among Android devices, even though HTC's implementation differs slightly from other skins and stock Android.
One thing I am concerned about is HTC's update track record. Pretty much every OEM that isn't Google has a somewhat poor track record of pushing out software updates and, most importantly, security patches. Judging by their support for phones like the HTC 10, HTC's record is above average, taking a couple of months to roll out Android 7.0 after it was released. Their phones continue to be supported into the future as well, though we'll have to wait and see what they end up doing with the U11.