I know this question is way, way, way late considering the release date of MMF2, but I've been away for quite some time. Is there a list of some sort, perhaps? Hopefully it's not one of those "too much to say" answers.
All problems can be solved through the use of violence and/or duct tape.
The three big differences:
* Hardware Acceleration - makes a *huge* difference to performance in Windows games.
* Exporters - it's possible to buy exporters for a very wide range of formats (incl. Apple and Android smartphones), with support for more being added all the time. This makes developing commercial games a far more realistic prospect.
* Support - as MMF1 is no longer current (and hasn't been for a long while), you'll have a much harder time getting help from other users - you're more or less on your own.
There are also more extensions, and various other differences as well, but they're really just minor enhancements - the points above are the ones that make it worth upgrading for.
There's also the really tiny things like the debugging feature and expression editor syntax highlighters which more than double your productivity
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.
They're what I meant by "minor enhancements" - they certainly don't double my productivity (maybe increase it by 5% at the absolute most), and they wouldn't influence my decision on whether or not to upgrade.
The syntax highlighting I don't find useful at all, and debugging was never a problem in MMF1 anyway (using lists/counters/debug console extension/etc). The MMF2 debugger doesn't really even help when you have multiple instances of an object (which is nearly always), because you don't know which is which in the list. Most of the time, it's easier just to create your own debugger, which takes about a minute.