Primary Use Case
Cisco ASA is born as an hardware firewall. The user case is security check on company's external connections (Internet and VPN access).
Most recent versions include antivirus and intrusion prevention to add security layers (including the above scenarios and the internal network)
Improvements to My Organization
Cisco ASA have been the main security device for many years, slowly replaced with Check Point on the main datacentre.
ASA is stable and with a low level of work required on the maintenance side. It is a dedicated firewall, so you do not have to manage additional topics like spam, web sites filtering and so on.The routing part is high level as usual with Cisco products.
Room for Improvement
You have to know the ASA command line very well because not all operations are available in the graphical interface (or let's say that sometimes it is better to operate with the ASA CLI).If you are searching for an "all in one product" it is not for you
No, stability is a really strong point with ASA.
No, an assessment about the workload is important to select the right device.
Customer Service and Technical Support
Over many year, the only kind of support we needed directly from Cisco was (really seldom) for parts replacement
The previous solution was based on software firewalls that where not able to perform as the Cisco ASA
Setup of a firewall, on a medium / large deployment is always a complex work.
Cisco ASA (more than other vendors' solutions) require a lot of know-how and real world expertise to be configured properly.
More than one external team (Cisco partners) has been involved over time.
All of them were outstanding in their work.
Positive. The devices serves thousands of users for many years, outliving other vendors solutions.
Pricing, Setup Cost and Licensing
Cisco devices are for sure costly and budget could be an important constrain on selecting them as our security solution.
Other Solutions Considered
When the choice was made, some comparison was made with other market leaders but integration with the existing Cisco network was a really important positive side in the final decision.
ASA is one of the the state-of-the-art firewall devices for security.
It is affordable and not too complicated to use if you are doing standard operations (modifying ACLs, natting and so on) on an existing deployment.
Disclosure: I am a real user, and this review is based on my own experience and opinions.