Funny, I just applied to global entry. I don’t really care about global entry, what I really meed is tsa precheck since I travel domestically a lot. But global entry already covers precheck and the fees are very similar so I went for it.

I'd guess that the vast majority of people who have Global Entry either paid for it using credit card benefits (most travel rewards cards have a Global Entry credit) or have it paid for by their workplace.

There are still marginal benefits of GE over Mobile Passport - more airports have GE, you get expedited service at land borders and at Canadian airports, and you can cut the standard line if the kiosks are broken. My favorite part of GE might be the reciprocal benefits you get in other countries though. For instance, you can sign up with the UK to use their automated border gates which is normally limited to EU citizens only.

Update: Tried out Mobile Passport on Sunday at JFK to bypass the Global Entry kiosks, worked a charm.

Spoke to customs officer for the express line handling both, who observed because of commingled lines and no kiosk, MP can indeed get you through quicker.