I've found OB is a really good scheme although a lot isn't written about it on FT.

As others have noted you can get seats on any flight which is hugely useful when there is no EC availability.

If you run your own business, and you/your staff do company travel on BA you should get this:
http://corp.americanexpress.com/gcs/...acardplus.aspx

It's a great deal as you get the BA miles when you buy the flights (3 per £) plus the travelling person gets their own BA miles. You as the business get the OB points and with the card above also get a 50% bonus of those OB points.