Reply to S4 + Midifighter, Pro's and Con's

I currently have an S4, but I'm looking to add on in order to get some more creative range.

So, if you have an S4 and a Midifighter, what are you using it for, and how has it helped improve your sets/recordings?

And also, is anyone using an S4+ Midifighter+ X1? If so, what for?

Thanks for your responses gentlemen, maybe you can help me in deciding what to buy next!