You are going to love Monster Bash, congrats on the purchase.
Mechanically i have had no issues with mine, but the playfield wear points are noticable on the drac arc and the mosh pit hole (u can get a cliffy for this) also the scoop cops a hammering.
My only real issue is the playfield lighting, it is quite a dark playfield, i would think that led's would fix that problem, but it will be interesting to see what you think about the lighting issue.
Enjoy, this really is a great pin.