Have you seen the screenshots with so many icons? That doesn't fit an iPhone 4S nor 5S for sure. Maybe on the 6 it's okay, but not less...
Is it worth it then?
Yeah, it's really too bad we can't get an iPad/6+ category.
I've heard lots of good things about this game, but haven't played it myself. If I had a functioning iPad, I'd probably have bought it when it was $4.99, and at a buck I wouldn't have even thought about it. If it weren't for the fact that apps & iOS updates tend to break things, I'd be tempted to buy it anyway in case I do buy a new iPad and/or jailbreak someday (you can change the device flags in the IPA file and install iPad apps on iPhones, albiet with display issues that change from app to app...)