Stayed with Heide for a month. Basically, it was great. Very central; I hardly ever used public transportation - in January! Felt quite homely. Heide herself is nice and extremely voluntarily helpful. Knows the city, its places and its ways by heart. Just as an example, it was she, rather than my university hosts, who told me that if they just write me a short letter, I could use it to get a humongous discount for public transportation. And in general she always had good München-advice, both for touristic purposes and for making it my temporary home de-facto. And sharing the place with her was convenient, too. For example, I need lotsa quiet or else I can't sleep, and she made sure I get it.
So all-in-all, I would definitely recommend the place, and am pretty sure it is under-priced.

p.s. finding a sim-card around to make up for the lack of Wifi is no problem at all.