I agree, not having a 16T cog does bother me. On my single bike with the 11-26 cassette, I have occasionally removed the 13T and put a 16T in instead. This seems counter-intuitive because the 12-14 jump is a bigger percentage difference than the 15-17 jump, but it makes sense to me because the 16T cog is right in the middle of the cassette where I spend a lot of time, while the region where the 13T cog has disappeared from I spend a very little amount of time, and so I miss the 13T much less than I do the 16T. No matter what, I still want to keep the tight spacing on the low end and have a decent top gear, so one of these has to go.

Everyone keeps saying that the new Campy gear going to 11-speed cassettes is pointless, but I would certainly appreciate being able to have one more cog in there, because then I wouldn't have to make these difficult decisions. However, I'm probably never going to use Campy because then I can't interchange parts between manufacturers (Shimano and SRAM mostly) and between mountain and road components very easily, and the cassettes won't fit on my current hubs. I've heard that FSA should be coming out with a full groupset soon-ish, and it will probably be 11-speed, so I'll take a long look at that once more details are available.