The DA*60-250/4 zoom was by good margin the most used lens on my trip. Combined with the K-7 it's adequate for many wildlife action situations. Consider this one, for example. The autofocus was set to multi-segment, and as all AF systems it tend to prioritise the brightest elements in the frame. Yet it had the wits to stick to the bird.
That said, I think Pentax still has a way to go with their AF system. I notice the K-7 is a big leap forward compared to any previous AF camera from Pentax when it comes to track-focusing, but there's still a good gap up to Canon and Nikon in this respect. And Sony too. To get a sharp shot in a situation like the above, one has to expect a considerable number of mis-focused shots. There's a lot of variables, though. White birds against dark background gives a good hit rate. Lower the contrast, and Pentax bails out sooner than the others. Try to photograph brown birds against blue sea and you're lost with Pentax. I threw away 90% of my pictures of giant petrels in flight obtained under similar conditions.
But then again... The main key to successful photography is to know the strengths and weaknesses of your gear. The K-7 has a lot of strengths to show for itself. And I think I'm getting better at catching these critters as they fly by, too.