I've owned quite a few of the DMD pins. Thanks largely to Odin and his great collection of EM's, I started to really appreciate how fun they could be. One of the things that I love about any pin is if it has that strong "just one more game" pull to it, that makes you want to play the game again as soon as it's over.
EM's have that in spades. As others have said, the rules are usually pretty simple to understand with easy goals. Simple to understand...difficult to master. I also appreciate the shorter ball times. My Sure Shot, set on 5 ball play, kicks my ass on a regular basis. Those 5 balls won't last as long as a 3 ball game on Iron Man.
Since you don't have music, call outs, a DMD, etc., the games are more pure in terms of concentrating on the silver ball. I do love the sound of the chimes/bells too.
I'm really glad that I've discovered how fun EM's can be. It's like another world of pinball...and the bang for the buck in terms of fun is extremely hard to beat for the price of admission.