Cisco ASA has a well-written command-line interface. Cisco’s AnyConnect SSL VPN is by far the best client VPN technology I’ve ever had to deploy and manage. Upgrades are a breeze. Failovers between units are flawless. FirePower add-ons deepen security with intrusion prevention (IPS), anti-malware protection (AMP), and URL filtering. These particular services can run as a hardware or software module within the ASA. Unlike ASA with CSM, these modules are managed by FireSight, a single pane for all of your FirePower nodes. It’s intuitive and easy to use, but still lacks some automation capabilities (e.g., bulk edits, etc.).
Improvements to My Organization:
Cisco is a huge name in the networking world. Having a solution that includes their firewall technology adds value from an operability and support perspective. Cisco, although sometimes considered to be "behind the times" with firewall technology, continues to prove it has momentum in the industry through acquisitions such as Sourcefire and OpenDNS, with rapid integration into their systems. Additionally, ASA is synergistic with other security offerings from Cisco, such as ISE, remote tele-office workers, etc.
Room for Improvement:
When running multiple firewalls in your network, you need someone to manage them from a central point. Cisco’s answer is Cisco Security Manager (CSM). Unfortunately, this is a suite of applications that is in much need of an overhaul. It is riddled with bugs and lacks the intuitive experience found in competing vendor offerings. The counter-intuitive interface makes configuration management cumbersome and prone to mistakes. There are software defects within certain modules of the application, resulting in a frustrating experience. Reporting is almost useless. The best part about it is the logging component, but it still is lacking, compared to what you get from other competing vendors.
Aside from management, I think Cisco needs to become more application-focused, something that a few of their competitors shine in.
Use of Solution:
I've deployed and managed Cisco ASA's for over a decade. I've used the X-series models for about three years now.
I have not encountered any stability issues; this is a solid firewall platform. Stability is where it shines.
The newer clustering capabilities have introduced some solid scalability design options. From a cost perspective, scalability is quite intimidating.
Cisco's TAC engineers are competent, responsive and typically resolve issues in a timely fashion. Do not use them for "best practice"; this is what channel partners are for.
I previously used Check Point. Check Point relied on a thick, Windows-based client and, at the time, did not support transparent contexts. However, Check Point has a solid management platform, which is something Cisco should take some pointers from.
Initial setup is complex for a new user, straightforward for a seasoned user. Tons of documentation is available, but you can easily get lost for days if you've never touched one. Cisco offers ASDM, a GUI wizard that can help set up the firewalls. This is nice for newer folks.
Cost and Licensing Advice:
Work very closely with your channel partners to verify you have all the licensing you need (VPN, Firepower, etc.). Pricing is always a challenge. Buy closer to Cisco's EOY and you might save a few bucks.
Other Solutions Considered:
Before choosing this product, I also evaluated Palo Alto. I really liked their firewall platform, their Panorama management platform, and wildfire technology. Their SSL VPN was seriously lacking. This is a decent option to consider as well.
Read the Cisco Validated Designs (CVDs) regarding ASAs. Find some decent blogs, discuss topologies and scenarios with a seasoned engineer, and get your final design validated by Cisco. Your Cisco SE should be able to assist with this. If you need assistance implementing, work with your channel partner.
Disclosure: I am a real user, and this review is based on my own experience and opinions.