Having a higher boil-off can indeed help with brewhouse efficiency. Because you have the opportunity to use more sparge water, you can extract more sugars. This can be especially helpful with big beers, where you may be already mashing thick just to get a single decent sparge volume and could...
Hard to pick a worst. There definitely have been some disappointing brews I've tried.
Most recently, grabbed a bomber of Lagunitas Lucky 13 (research). It's pretty highly rated, so I probably just don't get it, but it tasted like licking the inside of my grain bag and then washing it down...
937.
Busted it last night while rinsing it off. It started to roll back towards the sink and I just blankly watched it tumble in and break the top off.
Had it for 5 weeks. Died so young.