The limitations are documented as foot/side notes.
Analogy: It's like seeing "ACID compliance!" on a feature list, then finding buried in the documentation that is only the case for single-document transactions in unordered collections on a single machine only.
The new feature might be useful to some but including it on a feature list without disclaimer is misleading.
Re:MongoDB 1.8 (stable) released
by thibaut_barrere on Thursday March 17, 2011 @01:46PM
(#2337114)
I understand your analogy really :)
Really curious: are you using mongo currently? Or browsing the docs?
Your mileage may vary as they say: I used the GIS since 1.6 and it was very helpful for me in this form already :)