I just got back from my first weekend meditation retreat led by Ajahn Cittapalo. I think one of the most important thing I learned there was that "there is no way to peace, peace is the way". In other words, it doesn't matter what you experience in meditation so much, just make peace with it (call it metta and uppekha if you like), that way you are creating good meditation kamma and avoiding creating bad meditation kamma. Even if thoughts and feelings based on the defilements arise it is better, in my opinion, to just be aware of them in terms of anatta and anicca rather than to identify with them and think "oh no I am a failure at meditation, I still have strong cravings, I still have lots of ill-will". Even when mindfulness isn't all that strong, just make peace with dull-mindedness.
Still nothing original to add to the topic, but for me it seems to be an important point that can't be over-stated.
Four types of letting go:
1) Giving; expecting nothing back in return
2) Throwing things away
3) Contentment; wanting to be here, not wanting to be anywhere else
4) "Teflon Mind"; having a mind which doesn't accumulate things
- Ajahn Brahm