While I have not installed one myself I have talked to a few owners who have the VSM 422 - they give it good marks. Probably the main reasons you see few of them are price and the fact that not everybody wants such a comprehensive product. Most would buy a good battery monitor like the Victron for $149. If you want/need to monitor tank levels as well as battery monitoring I think it is a good choice.
Here is a link to a Panbo review of it. Panbo: The Marine Electronics Weblog: Blue Sea VSM 422, economy monitoring
I have found every Blue Seas product I install to be excellent. Blue Seas also has excellent product support if needed.