How fragile is my Mustang "Pro Guitar" controller?
I also have a Mustang Pro Guitar and it's far too new for anyone to tell if it will be durable or not. I would give it the benefit of the doubt and assume it will be durable until the community proves otherwise.
In other words, check back here in a year. :)
Also I found the guitar almost unplayable without a pick. My fingers are nowhere near precise enough to hit specific strings.. so I always use a pick, and the guitar manual recommends you use a pick as well (the guitar itself comes with 2 picks in the plastic bag containing the manual.)