I've actively used C2 for 2+ years and released a game to Steam. Was totally happy with it during developing my game.
But i got into some really heavy technical troubles while putting C2 game into Steam. Like i had to manually edit EACH exported build to add increments (like --ignoregpublacklist etc). In C3 i did it only once at the export screen.
Also lots of quality of life features were added in C3 like visual array editor and global search (which sold C3 to me - it saves MONTHS of work time even at medium sized games).
About the deals, as a C2 license holder i got 50% discount for a year of C3 - awesome deal, if you ask me. It was time-limited, and ran for several months or even longer.
People tend to say that 100$/year is much. I'll tell you that it's GENEROUS and HUMBLE. Average C2 made game makes 100$ a month (actually lots of steam indies earn that much disregarding engine used). Of course, you have to create that average game first, and release it on Steam.
So yeah, as for me C2 outlived itself and technology moves forward. Even creating a game you can get into position where scrapping a project (or parts of it) is the only reasonable way to move on. So i totally understand 
Ashley and 
Tom.
C3 is already lots better than C2, thanks to dropping aged code parts (was explained in one of Scirra blogs). You feel bad for paying 100 bucks for C2, while you already payed for C2 5 years ago? It's capitalism, ok? Or you want Scirra to maintain C2 until they die of hunger? People have to pay the bills, you know.