Observium's niche is user-friendly software for comprehensive monitoring of networks (and some server/appliance things). Setup is as easy as Wordpress and it will monitor pretty much everything on a network (ISP/carrier). Adding a device is pretty much one click, add hostname.
In exchange it expects things like having resolvable hostnames for devices and standardized port descriptions.
Compare this with Nagios or Cacti where you have to configure checks/graph collection for each thing you care about. The skill level required to set them up is a bit higher than Observium but still free.
Alternatively you have commercial software like Orion or Intermapper where setup may be easier but you have to pay for every metric you collect.
Because of this Observium gets a stream of vocal small MSP/ISP-type people who demand support and aren't willing to pay for it. I believe Obserivum went to a pay-for-access model in part to keep this under control.
I use Observium, pay for the subscription (~$200/yr is really trivial for this), and have contributed patches (that were committed) that fixed bugs and added device support (without any compensation aside from it making $DAYJOB easier). From the WISP community alone I saw probably half a year of "I won't buy a subscription until you support X device/X pet feature" from people who often came off as the client from hell in how they said it.
So, yeah, I don't like that I end up with a bit of anxiety over the reception my patches will get but I see the occasionally rough reaction as a immune response from a community that's under stress.
…I'm not pointing in any direction… ducks
-- http://observium.org/wiki/Edition_Split#Observium_Community_...
I do agree with dozzie though and that's something LibreNMS hasn't yet resolved which is being able to correlate data from different devices / systems to give you the one true answer of what's just gone wrong. I'd like to think we could get closer to being able to do that with more people contributing + some fundamental changes to the software.