From all the firewalls we have worked with, the Cisco ASA 5500-X Series is the most reliable one. Management can be done via both command line and GUI. High availability is on of the strong points. VPN is also included and we are able to connect all our remote users to our internal network and resources with that! Review collected by and hosted on G2.com.
Managing the ASA 5500-X Series via GUI can be a bit confusing if you also use command line for management. Too many object-groups are automatically created. If you only stick to the management via GUI this is just fine. If you want to do both then this is getting confusing. Personally I think that management via command line is much more effective once you get used to it. Review collected by and hosted on G2.com.