Between you and Last Sinner, I decided to finally start watching Mysterious Girlfriend X. And I have to say that I really liked its first episode! I'll probably post on the series thread for it after I've watched the 2nd episode.
I like the romantic pairing here, and I like how it's really their story. No love triangles, no harem shenanigans, just a normal (but creative/imaginative) guy and a cute (but in a different way, and quirky) girl.
That being said, much of anime entertainment really is simple wish-fulfillment, and I see no harm in giving fans that option once the core work is complete
For other mediums I always say that that's what fanfiction is for but with animes being adapted from VNs with multiple endings and Gen Urobuchi starting out as a VN writer I can understand.
I just personaly have a hard time separating the "main work" from whatever is done on the side.That's why I havn't looked too closely into the madoka PSP game,kinda scared it would negatively impact the anime for me.
I think that a better way of putting it is that Sayaka and Noe's respective falls was integral to the core message and theme that Urobuchi and Okada were aiming for respectively. So while giving them happy ends would be nicer, certainly, it might also undermine what the writer was aiming for at an overarching level (this is especially true of Noe, I would argue).
That being said, much of anime entertainment really is simple wish-fulfillment, and I see no harm in giving fans that option once the core work is complete.