Media reports say that EADS/Airbus is poised to launch the latest version of the A350 very soon. So I thought this would be as good a time as any to summarize the Boeing view on the "XWB" based on the limited information we've seen and heard so far.
In general, the new A350 offering is an improvement over the existing Airbus A330 and 4-engined A340 families. But the A350 still lacks answers to several key technological questions for an airplane entering service as much as 8 or so years from today.
In addition, Airbus is trying to cover the very broad 200 to 400 seat market with just one airplane family. Something that is very difficult to do. And it leaves Airbus basically with no entry in the sizeable 200-250 seat market (where the 787-8 is positioned). About 1,500 airplanes of that size will need to be replaced (A300, A310, 767).
Obviously our views on the A350 are based on what Airbus announced at Farnborough earlier this year. I expect there will be more changes to the design, because the current configuration seems to fall short of what the market is looking for.
The 777 and 787: still the perfect combination - depicted here as they might look parked together at the gate in the near future.

Airbus has previously released some information on seating capacity, range, and economic comparisons vs. the Boeing 787 and 777, with little technical detail to back up their claims. Even by 2015, Boeing doesn't foresee the availability of technologies needed to produce an aircraft with the capabilities and economics that Airbus was advertising at Farnborough.
And one of the important things to keep in mind as you hear about the A350: Airbus compares each A350XWB model with a Boeing airplane that is significantly smaller, rather than comparing like-sizes. This has the effect of distorting the per-seat efficiency comparisons to their advantage.
For example, Airbus compares the A350-800 at 270 seats to the 787-8 at 242 seats - a 28-seat differential. A more appropriate comparison is with the 787-9 which seats 280 - a 10-seat differential.
Something else to remember: Airbus is comparing the relative efficiency of the A350 - not due to enter service until sometime after 2012 - to today's versions of the 777 family. But Boeing continuously adds technology to the 777 product line - note the recent introductions of the 777-300ER, 777-200LR, and 777 Freighter - and we'll look to further improve our twin-aisle products by incorporating the latest technologies.
And as I've noted before, there is a market for more than 1,400 new airplane deliveries between now and 2015 in the 200-400 seat market. What airline can afford to wait?
Finally, you ought to view the "XWB" label with a bit of skepticism. While the A350XWB may claim to be 3 to 5 inches wider than the 787 (which adds little to no value), it is 10 to 12 inches narrower than the 777. I still don't quite get the claim of "Xtra Wide Body" when 2 out of 3 of its models compete directly with the 777, which is significantly wider.
So, having summed that all up, I will now turn my attention to working on an extra wide body of my own. I'll be feasting on the traditional American Thanksgiving turkey dinner tomorrow!