This one goes back a few years, but still has something to teach us all...
Back when I was church treasurer, the desktop software we used was fine, but clunky. I grafted multi-user capabilities onto the single-user package by checking the software into SVN and launching it from a script which grabbed a lock before updating and launching. Then at the end, it would commit with a progress bar.
This all seemed a bit hateful (and yet is still in use and working well, nine years later), so I looked around for something modern. The ideal solution would be web-based, so it could be used by multiple people from different systems, and not tied to a single OS (i.e. Windows).
Paxton Charities Accounting is "the other one" in this nice market, and we tried moving to it. Their website notes that both their desktop software and their "online" version have exactly the same features, with seamless migration between them - no small achievement, and one I was professionally curious about...
It only became apparent to me once we'd signed up for it how they achieve this - and the stench of genius almost made my eyes water.
Their "online version" is the desktop software, but you launch it over remote desktop from a Windows server at their end!
I'm still torn over whether this is very clever or very nasty - it certainly killed my hopes of being able to use this stuff on Linux* or mobile clients, though in the end it was the rather clunky 1990s feel to the software, a significant step backwards from what we already had, that made us decide not to go with Paxton. The robust quarterly costs were noticeable too (presumably quite a lot of it going to Microsoft for the terminal server per-client licensing).
*Yes, there are remote desktop clients for Linux, but I never found one which coped with the SSL used by this particular application.