If you're not worried about bureau pulls, go ahead and get at least one Discover account for each person in the household - then you can maximize the quarterly bonus. At 5%, it's easy to hit the $20 minimum to redeem and the "value" of their currency has been discussed already in the thread. At the very least, a 1:1 statement credit.

But as stated, I wish the 5% caps would be raised. $800 on air travel - even with web specials, that's only a few flights! We want more!

Also, tip for the 5%s... if you aren't going to spend the full limit within the quarter, but regularly use that category/merchant, get a gift card before the end of the period and use it at your leisure. We did that last month with the Warehouse Club promo (Sams GC good at Sams and WM).