SonicWall NSA is best suited for small to mid-size companies or small to medium K-12 school districts. It's less appropriate for larger businesses and schools. This is due to their ease of use and well-rounded feature set but lacks in advanced configuration, performance, and reliability.
The usability takes a bit of training, like any firewall, but I've found that showing even Tier 1 helpdesk how to do basic things has been easy. We have entry-level IT technicians performing white-listing, IP entries, VPN access and LDAP functions, to name a few tasks. The menus in the GUI are pretty straight forward.
Most of the time, calling SonicWall NSA Support, you get an expert who can help resolve your issues. RMAs are pretty easy once they determine there is an issue with the hardware. Support is available 24x7, which makes emergency calls easy. The only downside is the support engineers may have thick accents; however, their expertise more than makes up for any language barriers.
The SonicWall NSA is a lot more fluid and much less clunky than a Watchguard firewall. The Watchguard is ok for a small business-- you can buy them at retail outlets. But as you can see above, this model of Watchguard Firebox has been discontinued. The NSA classes are a more high-end and functional business-class firewall.
