IPv6 migration steps for mid-scale isp

[Fredrik Sallinen <fredrik.sallinen () gmail com>]

Hello,

Recently we have decided to start IPv6 migration in our network. We
have ~1K BNGs and connecting our customers to network using PPPoE.
I'd be interested in hearing from the technical community about their
experiences and recommendations on this process. I'm wondering:

Shall I go for IPv6-only deployment or dual stack?
Where to start with IPv6? (core, edge or ...)
What are the best practices for ISPs?
What are the costs and return on investment?
How to identify address CPE and legacy application issues?

Fredrik