I have this game on CD (and on GOG too when I accidentally bought it). Question: Do I need the community patch if I want to play off the CD?

I'm usually very much against any fan made patches on my first run of the game (I try them on subsequent runs if they're good), but I do make exceptions if they're absolutely necessary. Making the game better, no matter how screwed up it was before, or fixing non-critical bugs is usually not a reason to install them; I want to play the game as it was (so just as an example, Grayface patch was a no-no for me). Only game-breaking or critical (like making whole areas unaccesible) bugs would cause me to install one.

So is that the case with MM9?

Incidentally, is the patch already included with GOG installation?

Yes, the gog.com version of MM9 is already patched to 1.3.

The GOG does have TELP's patch, but even with that it still has major issues. There are other files that need to be replaced for it to become manageable. The multiple posts about MM9 makes it pretty clear that it was never properly finished.

bump. Anyone? I know the game has bugs (even after the patch). But how unplayable is it without any patch at all?

I finished original version v1.0. GOG version is patched, fixing all of gamebreaking bugs. The only issue is with the time it takes to enter character screen, but I posted a fix somewhere on this forum, I didn't try it myself, but it works for other people. This game is very playable, it just doesn't really stand up with other MM games, but as a standalone game it is quite decent.

To be honest, if to compare GOG's MM9 with some of the modern games, MM9 looks like the most polished game ever.

I won't be playing GOG's version but the 1.2 off a CD.

How was 1.0?

1.0 had 3 gamebreaking bugs, which were fixed in 1.1/1.2 - one in Anskram Keep, another with ice giant quest and another with getting approvals. I was lucky to not trigger those bugs, and I didn't have any issues with finishing game (except one puzzle which made me stuck for hours).