I got a pro specifically to avoid the hammer issues. I've heard about them enough that I just didn't want to bother. The pro still plays amazingly, and you can add spinners if you're crafty or order from Pinball Refinery. My pro has had next to no issues. My left slingshot would sometimes fire randomly. I opened the switch up a little bit (bent it gently) and now have zero problems at all.
Regarding new or used; I like new things so I bought new. Went with Pinball Refinery because I wanted a ton of mods but didn't want to do all of them myself.