Tracking the health of your servers

Continuing the topic .

I will be brief: what, in your opinion, is lacking for such services as basicstate.com , host-tracker.com , mon.itor.us , etc.?

Maybe you have your own software in your inventory, but would you prefer to use a service with wider functionality?

Do you need diagrams and similar “complex” structures on such a service, or is it enough to just write about some problems with the servers?

I'd like to hear the opinion of admins.