Support, support, support
The number 1 problem with Cisco's DevNet is support.
The developer forums are like a barren wasteland with people asking questions and no-one providing answers. No Cisco employees hang out there and few other people are able to answer questions. (Contrast this to the main support forums with plenty of helpful people and Cisco employees)
You can log a support call with Cisco: Providing you pony up $2,000 for the entry level developer support. When you do manage to pry the credit card out of the boss's hand and log a support call, they're not fast at getting back to you. It feels like the support engineers know no more than the customer.
Their API documentation isn't bad - except for the documents that require over 2GB of free RAM to open.