I like what prettyflyforawifi has contributed. With the Solarwinds pricing model, they do tend to squeeze you. It is efficiently priced for my specific environment because we are using it at a way larger scale than it was ever designed for, and we have been able to make the most of their unlimited licenses. The downside to what we are doing is that we have had to create our own solutions to the lack of multitenancy.
Another great point was that the web interface and the integration of different acquired monitoring tools can be frustrating. The NPM web interface is great, and they keep improving it. Also, they finally came out with a web-based report writer which is sleek and powerful compared to the server-side tools it is replacing. It all breaks down, when I have to use SAM. SAM serves a purpose that Solarwinds really does need, and I am excited that an optional SAM agent is on the roadmap. However, they bought this thing and bolted it onto Solarwinds and it is painfully obvious / frustrating. The database is structured way differently between SAM and NPM, and the potential to work in bulk barely exists. We have been able to create some cool custom reporting tools for NPM, because the database structure is very straightforward and we can build a lot of our own SQL queries to pull from it. The SAM database is very differently structured, and trying to query it is not as easy. There is also a strange anomalous relationship between 'Applications' and 'Application Templates' that Solarwinds has never properly defined. Worst of all, the SAM website is atrocious. Many of the lists and drop down menus sort items by their date of creation, not alphabetically. This makes navigation a nightmare. We have had to adopt a specific naming convention that includes the node name and enforce a strict 1 template per application rule to create some order. So if we have to make adjustments to 20 SAM Templates, it requires our lowest ranking guy to go in and commit those changes one by one. This is even more frustrating because our lowest ranking guy is me.
I don't consider myself to be brand-loyal to any product either, but I like what I see with about 80% of Solarwinds. For basic up/down/cpu/memory/volume monitoring Solarwinds or Nimsoft would work great. Nagios is another strong contender too.