Re: Skype for business is pretty sad
1. Can't say I've ever really seen that problem. Windows do tend to shuffled about a bit if you start using meeting content i.e. presentations or desktop sharing but for IM calls I've never had a problem.
2. That's not a Skype for Business/Lync issue, that's a "Bluetooth is crap" issue. I've yet to come across a Bluetooth headset that qualifies as "very good" or better, when used with Skype for Business or not. Personally I have a Plantronics Voyager Legend UC ML headset that qualifies as "good".
3. That will very much depend on the setup of your PC. If your Bluetooth device is one of those fancy ones that comes with it's own dongle, then the audio driver may well be attached to the dongle not the headset, so Windows is unaware when it disconnects. If it is through normal Bluetooth adapter, then the audio device will cease to exist, and admittedly Skype for Business could tell you when that happened. As for low battery notification, again that's the devices responsibility as there is no proper standard (or at least not on that that's used in Windows or Android) within Bluetooth for notifying the host about the battery state.
4. Never seen that myself, but most likely down to QoS? HD quality audio has always worked fine for me whether internally over the FrontEnd servers or even coming in via Edge. WiFi has presented some issues but we've solved those now.
5. They can be, but it depends how much money you spend. Sennheiser and Plantronics do some nice Lync Certified wireless headsets, but they cost a small fortune. There's no reason you have to user a certified device though, there's plenty of good uncertified devices.
6. Mostly agreed on this, it's not great.
7. Personally I've never had a problem with the UI, either the old Lync 2010 and 2013 UI or the new Skype for Business 2016, and I've not had any users I've had to show things more than once.
The backend UI on the server on the other hand.... Still uses Silverlight for the main part of the web GUI, uses another crappier web interface for configuring response groups, and has no GUI at all for configuring Common Area Phones and some other things. If any part of the GUI needs work, it's the server side.
Also as for what the article says about "the directory search will find new contacts by their Microsoft account address, but never by their Skype name." That's not exactly true, you can add a Skype user by their Skype username by entering it as email@example.com this has been the case for a number of years and was introduced in Lync 2013 Server before Skype for Business was even a thing.
Skype for Business could certainly use work, both client and server side. Some bits of it are even questionable as to whether they should be in production use. But overall it's actually quite a good system, and has a great deal of potential. Just don't blame it for the failings of your hardware or OS, or your network infrastructure.