For e-Rewards: To find out if you can redeem your e-Rewards currency for US Airways...

-Login to e-Rewards
-Click on "Rewards" on the top tab
-Under the list of "Sponsor Rewards" you will see a list of companies.
--Is "US Airways" one of those companies?
---"Yes" then you should be ok. Just earn $25 and cash it in
---"No" then you can't earn a hit for GS with that account. Sorry.



For e-Rewards: To find out if you should sign up for an offer using a "Non-US Airways" invite...

-Who is sending you the offer?
--If it is Hilton, PriorityClub, or bmi (I think) = sign up NOW!
--If it is Delta, Emirates, or e-Miles = No joy! (You still could sign up, but can't get a hit in GS)
--If it is someone else... ????? (if you have any data points out there in FT land, please post 'em)

As always, YMMV -- this is just what I have seen and what I have read on this thread.