The price! Spiceworks is free, and has a great feature set for a free application!
The core aspect of Spiceworks or us is the helpdesk software, the classic or new ticket views both do great work, we've stuck with the classic views because it's what our customizations work best with and what our team is most familiar with still.
There's some serious limitations when it comes to growth. Approaching 20,000 tickets and the software is showing it's downsides now, it's a bit slow to search for users/tickets.
We're definitely at the stage where we are outgrowing Spiceworks now, and will be moving platforms sometime soon, but Spiceworks has been instrumental in allowing us to grow from where we WERE to where we ARE. The fact that the service is reliable, and free, has been great along the way, but now there's not much we can do to optimize and continue to move forward, but it's served us well for 6+ years now.
Definately give it a solid look and install, it's free, so you have nothing to lose!
Install on a test environment or a VM and run wild with some testing, setup portals, test features, network maps, etc. If it looks like it's going to be beneficial go ahead and roll it out and then add your real data to it.
We solved the fact that time entries were logged separately from issue resolutions, and Spiceworks lets us unify that in one place.