I like EMs and SS games where the pops are out in the wide open. They can be randomly punishing yet help you complete objectives. Think DOLLY targets on Dolly Parton, the drops on HOT TIP, etc. I also love a good center pop or an arrangement like Old Chicago.
Most pops feel like a waste of space on the playfield. A few games require you to shoot through them, which I find to be a great use of them. Funhouse handled it really well because there are times you want to cleanly shoot through them and times you want the ball to bounce in the pops. Houdini has a lot of issues, but I like that there are different ways to shoot through the pops for different rewards.
The pop on TNA is a thoughtful use. It's more interesting to shoot than a stand up and it's positioned in such a way that that it's not super punishing.