Here is my last entry the QCon San Francisco 2012 Lean UX track. I found Jeff Patton's talk on CoMaking great product very eye opening. Jeff argues that a surprisingly large percentage of the software we build does not end up being useful.
Being agile or lean is not enough and having a high velocity might just mean that we can produce more crap at a faster pace! Dividing the business and the developers often only help us blame each other when things go wrong. We should instead take joint ownership in the product and both bring our ideas to the table.
I can't find Jeff's slide but his website has 12 emerging best practice for agile UX as well as a lot of good related content that echoes ideas that were discussed in Jeff's great presentation. You can also check out the comaking website which has good content including Jeff's articles from above.