Care to go into fine grained detail about EXACTLY how the cold storage works and is architected/engineered? I don't see much useful content on the site regarding the feature, so, being a system architect myself, I would not trust this unless I knew what level of redundancy of service you are using. The following would be good to ensure:

• Are the servers (web/app/db/file) setup for High Availability with at least N+2
• Is the core infrastructure network multi-homed and are the servers and switches/routers all setup with bonded/trunked connections
• What RAID level are you running to store the wallet files, with what level of parity(double or triple), and are you employing a file checksum system like Tripwire to ensure any compromised files can be reported on
• What OS are you using on the systems to ensure you aren't hit by a microsoft-only worm or trojan?
• Is your network (on each system and at the border, DMZ, and core) hardened via VLANs, Port Filtering, IDS/IDP
• Are you duplicating/replicating data off-site with encryption on the wire and on the filesystems?
• What is the process/procedure for human interaction with the wallet files and methods used to securely handle their contents?
• What level of SLA are you assuring for this service - since you are dealing with monetary funds (as much as BTC can be defined that way), people will want to be sure they will absolutely get a response to their requests and services within a specific time frame.