- Yes, it's worth it to get a set of copper mugs. If properly taken care of (I've had one of mine for 4 years), they keep beautifully and pay for themselves quickly.
- I make all sorts of cocktails in mine - vodka soda with lime, dark and stormy, baileys and iced coffee, etc. Just not hot drinks (there are certain mugs that hot drinks can be made in)
- My favorite shape is the barrel shaped, mostly for aesthetics. However the most versatile one is standard shape, maybe 14-16 oz. I like the hammered style. I also have mint julep copper mugs that are awesome because they don't have a handle and are bigger.
Someone mentioned the lime reacting with the copper... the company I have bought from coats theirs in a lacquer that protects from that and it helps keep the copper nice over time. The company is Alchemade.com (I think they are on Amazon, too, if you have Prime) - they have a good variety. Pure copper mugs, and lined mugs (stainless steel, nickel, etc). Hope that helps.