Hi,
Thank you for posting in Symantec community.
I would be glad to answer your query.
1) How is support?
--> Symantec Endpoint Protection support is availalble with multiple options like Phone Support, Chat Support, Social support & Web Support via MySymantec
https://www-secure.symantec.com/connect/blogs/symantec-endpoint-protection-chat-phone-support-social-support-web-support-mysymantec
2) Is Symantec responsive to issues?
--> Yes, it will be.
3) Do they take ownership of problems?
--> Problem isolation will be always there, if Symantec is causing an issue support will definitely take the ownership of problems.
4) Does the product do a good job of protecting against advanced persistent threats?
--> Advanced persistent threats (APTs) pose serious challenges for organizations of all sizes. Challenges related to advanced persistent threats include cyber attacks that are designed to do anything from steal sensitive data for financial gain, corporate espionage, etc., to sabotage of critical infrastructure. These attacks are specifically targeted and are often carried out using sophisticated malware. The effectiveness of traditional file-based antivirus scanning technology is not by itself sufficient protection because a given malware associated with an APT will have extremely low prevalence, that is, will not be widely seen on the Internet. Traditional antivirus signature-based scanning is reactive in that a signature can only be written to detect a threat that has already been seen.
Symantec Endpoint Protection 12.1 (SEP 12.1) includes protection technologies that go beyond traditional antivirus scanning to provide effective protection of endpoints against the sophisticated malware used by APTs. This paper provides guidelines on how to ensure that SEP protection technologies are enabled and functioining in order to provide best protection for endpoints.
Additional Symantec Offerings to Protect against Advanced Persistent Threats
Symantec Endpoint Protection is just one important way to protect against advanced persistent threats. Symantec has additional offerings to help customers stay protected from advanced persistent threats. These include the following:
Symantec Critical System Protection
http://www.symantec.com/critical-system-protection
Symantec Web Gateway
http://www.symantec.com/web-gateway
Symantec Messaging Gateway
http://www.symantec.com/messaging-gateway
Symantec Managed Security Services
http://www.symantec.com/managed-security-services
4) Has the product helped you identify security issues in your system?
--> It depends upon the configuration of product. I would recommend to run triaware to get feel of any product.
5) Are whitelisting features easy to manage?
--> SEPM is easy to manage, to know about it's features like whitelisting, System lockdown takes time at initial configuration however it provides extra layer of security.
Best Practices Guide to Application Learning in Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH134367