I would not write off
mobile users as a small group.
A mobile user is any pilot who has filed a flight plan at home, flown somewhere, stayed there doing some variable-time task (so he could not file the return flight plan from home), and then he has to file the return flight plan using some mobile means.
And somebody flying a multi-leg trip will definitely not be pre-filing.
It's of course true that there is wifi, internet cafes, etc. But things have moved on since the heyday of unsecured wifi and - where you can get a connection at all, which is basically nowhere outside city centres i.e. most airports!! - the whole business has become a giant ripoff, with £20-40/day billing and potentially recurring CC charges. Internet cafes are the last place you want to search for in some strange town, and most of them stink of fag smoke, never mind the smashed up keyboards. And one cannot run the AFPEx Java app on a typical locked-down cafe computer, which leaves own-laptop connection, and I know only too well that most cafes don't allow a laptop connection. All doable of course (cafes and bars with wifi etc) but what a hassle.
On more than one occassion (like landing somewhere where they won't sell you avgas, alleged lack of PPR, etc) I have had to file a new FP from the cockpit (on GPRS/3G obviously - no wifi on the apron).
That leaves the departure airport, but filing a flight plan the old way (handwritten form) can be another hour wasted, messing around a non English speaking airport. Once one gets out of the English-fluent countries, at most "international" airports one is hard pressed to find anybody who speaks English, and in that I include the "tourist information" desk
This is why, 99% due to the "application download" uncertainty, I still maintain a 37 euro/year Homebriefing.com account, but it almost never gets used because there is EuroFPL (which only does IFR which is no good for 99% of UK private pilots). Also HB have trashed their website by using some trendy designer; 2MB of data last time I checked.
The other 1% is that AFPEx only just about runs on GPRS, and GPRS represents the vast majority of mobile data access; 3G has poor coverage outside city centres etc. I was running it on GPRS today; it did hang in there but only just. I think the timeouts need to be a bit longer.
One could argue mobile FP-filing users are a small group, but FP-filing pilots are a tiny group anyway; you don't "need" FPs for the UK. Yet plenty of people do file flight plans... enough to create work for loads of people in the now-closed FBUs... (reportedly 3000 flight plans per month) and they must be going somewhere.
Anway I know I've ranted on about this enough, and it's good to hear you are listening
Mac users are a totally different group - purely fashion conscious people with loads of money