Those are sweet, and I have quite a few left from a kit that I bought from Fastenal. The kit I bought was pretty spendy so I try to use them on the exterior lighting and really important shit that I dont want to see again. I still use the 3M heat seal crimps for just about everything else. I have some great crimpers, so I trust those connections.
There was a time I would butt splice anything. But not many teenagers understand the long term issues with such a repair. I still have drawer full of them but that is because I refuse to use the damn things. I suppose they have a use some where. I like the repair in that link. But I have gotten tot he point where I sodder and heat shrink everything. I prefer to run a whole new wire, but sometimes that is not feasable.