Overall I really enjoyed this collection, but like any anthology, there are going to be some that don't work for everyone, and I think this was about 50/50. I don't mind not digging a story overall, but when those stories take up so much room, eh.
The Steve Parker stories are probably the most fully "formed," in my opinion (because it seems they were written with the "Deathwatch" novel in mind, or possibly after it?), but my personal favorite was David Annandale's "The Varago Fastness" (sp?), which featured a lot of chapters from the "cursed" 21st founding. I'd never heard of this before, and found them hilariously fascinating. I hope those characters come back somewhere else. The first like three or four stories are very workmanlike, no risks taken. I felt they should have been scattered throughout more; the middle of the collection seemed to have all the 'risky' bits (i.e., Kryptman operating on a tyranid for the first time ... which barely even fit into this collection ... or a group of Tau encountering a nearly dead alien species and ... one ... half-alive Deathwatch member -- though I enjoyed that story, so I won't say anything negative about it).
I think this did what a good anthology in a universe like 40K should do: it made me hungry to find out more about a lot of the facets talked about here (mostly I want more Black Dragon / Flame Falcons action), and introduced me to some authors I'm now excited about, and let me know I dislike a couple of others. Great stuff.