I don't believe there are any "holy grail" companies left out there any more. I have a few buddies in BA, and they are very happy. The one thing to consider about joining any European flag carrier (and I'm not talking about Virgin here. :-), is that they are under a lot of strain to uphold the old traditional competitive packages. No doubt, working for a flag carrier will give you the best overall package. But there's been a lot of pressure from the LCC's in recent years, but they've always had their fairly large long haul segment to generate income. Now the pressure is also arriving on that segment. Carriers from the Middle East is dead set on gnawing away on the European carriers' traditional routes (the kangaroo route amongst others).
What has this got to do with the OP, you ask? LOTS. I missed the boat (ie I felt I was too old to wait 10-15 years for command), but I would've loved to join. However, if you join now, you are probably looking at a 25-35 year career prospect. I don't, for one minute, believe that the stories you hear about BA (and other flag carriers) today, will hold true throughout a career.
Holy grail? No! As close as you'll get to the holy grail? Absolutely yes!
If I was in the start of my career, I would join in a split second. If what I've written above is wrong, you'll enjoy a fantastic career in one of the greatest carriers in the world (IMHO). If I'm right, you can ALWAYS go down the contract/expat path. In fact, the latter is almost always a one way street.