On its own, it's a solid choice for an SMB or Mid-size Enterprise if you're price sensitive and looking primarily for core functionality. SolarWinds has a large family of products that can also be leveraged in conjunction with SWNDM. Turning the product loose on a very large environment for discovery and mapping should be done with care and concern for a number of reasons but including the performance of the product for this task. If you're looking for an all-in-one product with some presumed supporting features built in (config manager, etc.) you'll need to look elsewhere.
The sourceForge speed test would be well suited in most scenarios. From simply measuring your speed when connecting to new networks to trying to diagnose network issues at your house, workplace or any other environment where you may have spotty internet connection. I'd say is not well suited to get perfectly accurate results if needed for any type of network monitoring.
MS is meant for windows monitoring and up/down for mostly everything else. Moved away from MS System Center. Now we have better visibility and management can get reports. The other teams have added Linux to Solarwinds and also see improvements in monitoring. Whether you use snmp (v3), wmi or some other credentials to connect to you system, Solarwinds will more than likely be able to manage and monitor it.
The main reason why we selected the SourceForge speed test at my job was due the company's heavy and aggressive website whitelisting. The sourceForge speed test was one of the few tests we tried that was able to work fine within our restricted network. Plus it was easy to ready, even to my boss.