Please my fellow FTers, your sage advise is apprecaited!

I have now earned my long-awaited goal: Million Mile Flyer status on UA. Just qualified on a NRT-SEA flight last week.

Now that I have Lifetime PremEx and Star Gold status, I'm beginning to think about what other airlines I should focus on.

I will continue to fly UA as they are convenient from my SEA base, but I am looking forward to trying other airlines as well. Alaska will remain my other main airline in the west.

Here's what I'm thinking...

My main destinations:
Tokyo
UA and AA both fly this route, plus NW, but I'm not really considering them. I could fly AA on this route, or UA's First Suite.

Europe
I'm actually thinking about DL and US and CO on this. All three are said to offer exceptional premium cabin service.

USA
A mixture of AK and US in the west, DL, CO, US, in the east, and AA and UA in the midwest should cover the country.

Living in the corner and doing mostly long-haul/int'l trips, miles are easy to come by. I'm thinking I can rack up 250,000 miles, going by past experience.

What do you think my best bet is? How are AA, CO, DL, and US?

Thanks,
peter