ASA Appliance is Good in which capabilities?

firewall and IPS features this link will give you all new features of ASA

http://www.cisco.com/en/US/docs/security/asa/roadmap/asa_new_features.html

Top10 ASA capabilities:

1) Its way of handling and inspecting two-channel protocols such as FTP and Streaming media.

2) its way of keeping track of and inspecting connections by building connection/translation entries and use these entries' parameters to defent against various attacks such as ICMP Smurf, TCP SYN, and DNS UDP attacks.

3) Its way of inspecting source validity by using uRPF feature to defend against IP Spoofing attack.

4) Its way of generating random ISN values on behalf of the sender to defend against Session Hijacking and Man-in-the-Middle attacks.

5) Its way of inspecting ARP to defend against fake ARP entries installation attacks.

6) Its concept of security levels to deliver out-of-the-box secured legs even without ACL application.

7) Its virtualization capability to deliver Split Firewalling functionality by dividing the appliance into several virtual firewalls.

8) Its optional modules to deliver additional services such as Content Security and IPS. (AIP)

9) Its transparent (Layer2) functionality by bumping the appliance in the wire.

10) Its Packet Tracer tool and IP SLA monitor.