Out of the box, Solarwinds Network Performance Monitor does an adequate job of monitoring the basics of your network. Things like Bandwidth Utilization, syslog capture and reporting, circuit outages, etc. However, If you REALLY want to get the information we crave, you need to buy some of the plug-ins.
You start out with NTA, Netflow Traffic Analyzer. Now you don't just know that your bandwidth is being consumed. You know WHAT is taking a big bite out of that ALWAYS important bandwidth. Is it legitimate traffic and you need to add bandwidth or is it frivolous and you need to block it?
Next, if you operate call centers you might want to add on the VoiP and Network Quality Manager. I'm unfamiliar with this but it must have evolved from IP SLA Manager, a product I loved for it's ability to tell me how well my voice traffic was moving across the network. It looks like they've added integration with Call Manager so now you can really dig down into those voice related issues.
There's another piece you may consider indispensable if you have a lot of apps running across your network; Server and Application Monitor. Now we're cooking with gas!
Nowadays, it's just not enough to know that you still have bandwidth available. What you REALLY need to know is, do you have bandwidth available to ALL your key applications? QOS might be dropping packets while you are blithely examining your bandwidth utilization, thinking everything is running smoothly.
While Voice and one or 2 other apps may be blissfully travelling down the carpool lane of your network, what about the rest of your traffic? Is it stuck in a traffic jam, staring hungrily at those empty lanes? You NEED to know these things. And that's where the plugins will make your monitoring get up and DANCE! And once you KNOW what's going on on your network, YOU'LL be dancing too!