As someone who has NEVER flown a paid business class ticket, and who has only flown in international first class once (they needed the space in biz to try and seat a whole family together), I would no. However, if I had a zillion extra miles in the account, I would do so b/c the marginal cost would be insignificant. However, personally, the difference between coach and biz is much larger than biz and first and so I for the extra miles I would need for a 1st class award ticket vs. a biz class award ticket, I would save the extra miles and use them towards a future biz class award/upgrade.