Here's my take; I play the pro on location quite a bit and just picked up a premium. Both versions are fun now with the current code and as someone else pointed out, the custom sound packages made really brought this game to the next level.
I had some issues with my crossbow out of the gate which was attributed to an over sensitive switch. So now that my xbow works, I've taken a real liking to it, but making a shot with it is very difficult but it is rewarding when you make a tough shot like riot or barn when those modes are lit and/or have a multi kill lined up. All in all, I could live without the xbow but like having it for the extra novelty.
The bg ramp really isn't anything special and I could care less if it was there or not. I enjoy it more though when I'm shooting it with the xbow.
The lighting is a double edged sword. Sometimes I feel like 'goddamn this game is blinding. But on the flip side, I sometimes feel like it really immerses you into the theme and zombie apocalypse. Really increases intensity like zombies are coming. I could live without it but again, glad to have it.
Having spinners is great! But not only that, there are decent added rules to the spinners unlike a lot of other sterns. So having the spinners is great and gives the player another feature to shoot for.
Walker bombs are really the biggest game changer. At first I thought they were no big deal, but the strategy behind them is HUGE. having the ability to know when you have enough walker bombs to start a multiball is game changing cause you don't have to start a multiball at that time. Instead you can hit drops, start modes, and progress towards last man standing. So you get a lot of added breadth with walker bombs and that single handily makes the premium a must for long term home owners.