If it turns into a glider when you shut the master switch off, that's a problem.
Ehhh... maybe, but I'm not so sure about that. Let me tell you why I say that...
I have an electrically dependent airplane - I need voltage for fuel pressure and ignition, not to mention nav. In my airplane I have dual alternators and a large battery. Either alternator can take the full electrical load of the airplane, and the battery is good for about 30 minutes with both alternators offline, in an IFR flight condition. The Skyview EFIS has its own backup battery and happily proceed on its own for 45+ minutes. So far, so good - that covers my risk assessment for electrical redundancy, others will vary but this is mine. Alternator failures occur, but rarely - and if I have a single flight that has TWO of them, and I can't get it down in the time remaining on the battery, then Jesus loves me and I ain't gonna fight that.
I have redundant power paths to my fuel pumps and ignition, completely separate from the normal path through the master. I can power those items normally through the master or from a hot E-buss directly from the battery with the master off - but I do NOT have them set up for automatic transfer, intentionally. If something goes that far wrong in the cockpit such that there is an electrical fire/smoke, or worse yet a major fuel leakage in the cockpit, then I *DO* want to be able to hit the master and make everything go quiet, and then troubleshoot critical systems one by one as I bring them back online - and yes I'm including engine power in that statement. If I blow a fuel line at the fuel pumps and start dumping raw fuel in the cockpit, I'm going to go cold and deadstick it somewhere in the interest of not making ANY spark and turning myself into a shooting star.
I suppose it comes down to a comfort level with airborne "emergencies" of various levels and how we each deal with them. I've had a few over the last couple decades. I do NOT want to be in a situation where a device fails, the automatic failsafe takes over and puts the backup on line, and somehow I am not alerted to that fact or miss an indication of it. If I have to take positive action to bring the backup online then I know what I have operating and what I don't and there's not a question of whether I missed it or not. When things start to go "nonstandard" in the cockpit, in my mind I will treat it as "minor" which means "Huhhh, it shouldn't be doing that, let's see here...." or "major" which means too many things are going wrong to troubleshoot simultaneously or the issue is too major to troubleshoot immediately - in which case I want to kill the master, stop EVERYTHING, turn the airplane into a glider which follows the known physics of flight, and then take stock of what we know still works. Preferably prioritizing the engine first.
Everyone is different, and we have different risk profiles, this is mine. I've seen me react under pressure enough times to know what to expect. I know precisely how I will react when cruising along at 15,000' and the engine quits unexpectedly - because I've done it. YMMV.
But, I digress.... This is about UL Power, which is something I like and want to see succeed.