No, they were on CO and United, but US Airways couldn't see them. And this was with 3-5 different agents who all said it is pretty common. I did notice that UA/CO flights in the next 1-2 months were available, just further out there were many issues.

Many other airlines have this with other non-alliance partners, most notably AS with AA and DL.

Looking on each FFP's award chart (Econ/Biz/First):
United (LINK):
U.S. to Europe = 30/50/67.5
U.S. to North Asia = 32.5/60/70

US Airways (LINK):
U.S. to Europe = 60/100/125
U.S. to North Asia = 60/90/120

Is UA one-way and US round-trip?

Yes, UA awards are one-way. There's no way you're heading to Europe in Business for 50K miles (with the exception of Flying Blue promo awards, but that's a different story ;))

Also note US Airways has off-peak redemption rates. Jan 15 - Feb 28 you can go to Europe for 35k roundtrip, and if you're a cardholder I think that's reduced by 5k to 30k miles. Which is the cheapest mile deal there is to get to Europe that I'm aware of (the FB sales have way more YQ).

is this only on US metal?

Yes, of course. Also keep in mind that some discounted *A economy fares only qualify for 50% mileage credit on US, whereas you can still get 100% on UA/CO (I'm thinking about SA, LH, but there may be others). IIRC, this is a fairly recent change. Considering that UA/CO allow one-way awards and US does not, I'd say that lately the US advantage has diminished.

Which ones, apart from AS? Any in Star? Since this thread was comparing US to UA, i thot it was to be noted. But I'm interested in hearing about other major airlines that do it.

In 2011, I'd go UA. Their route map is far larger than US and even though they're alliance partners, things are always a little better on your "native" metal.

UA has low fees on awards, flexible one-ways, and E+. And when US craters (which I think it eventually will), there's a decent chance that regulators might allow AA to absorb it, not UA. So that could throw your stash in the direction of Oneworld, not *A.

Only "pros" for US are reduced award levels for CC holders and apparently less Starnet blocking.

Last week, four of us flew MCI-YVR (with connections), 2 on US roundtrip and 2 on UA/AA, one-way on each. The UA and AA segments all performed fine. Both US directions where canceled due to "aircraft availability". (No real weather issues anywhere.) And at the airports, the US people were disorganized and unhelpful. We weren't auto-confirmed on later flights the way UA and AA do. We couldn't even use a kiosk to rebook. We had to find humans to talk to, which was a challenge. Simple tickets, US metal, ticketed by US. It just seems that operationally-speaking, this is a dying company. I know it's just one experience but I've always felt like UA handled irrops in general better. Overall, it seems like a more robust company better able to adapt to day-to-day challenges of running an airline.

I know I would never want to fly US regularly, even with top-tier status. UA as a 1K was fantastic and UA as a lower elite is still not bad.

However, conversely more fares flown on US metal qualify for full mileage credit on partner programs than UA/CO. Take my favourite *A program Aegean for example, all US flights count as 100% mileage, but most discounted UA/CO fares only offer 50%.

UA do offer one-way awards, but no stopover on those.

But wouldn't that imply that the OP is considering setting up his primary *A account on Aegean? I mean, I don't disagree that it's a benefit, but it sounds more like a benefit to flying US metal vs. UA metal if your native program is Aegean.

(I know nothing about Aegean...feel free to correct me if I'm misunderstood this.)