For copper-to-copper, I think I'd still be partial to sweated joints, but I can see the appeal for copper-to-CPVC or copper-to-PEX. I also agree with Howitzer that it might be a great idea to keep a few pieces around to quickly handle the unexpected (I could have used a couple of caps a week or so ago as a stopgap during an unplanned water heater replacement.)

As far as sweating joints is concerned, I think one has to ask one's self: WWHD? (What would Hephaestus do?)