It depends on what you can get the tickets for. The value that most folks tell you to assign to frequent flyer miles is $0.02 per mile. That means that if you have to cash in 40K miles to get a ticket to Europe, then if you can get a coach ticket for less than $800, I'd pay cash -- or actually charge the ticket to my mileage linked credit card, get Citibank to give me a month loan, and then pay it off but I digress.

I wouldn't sweat the coach/business/first class thing too much if I were you. If you've got the miles to go business or first, then go ahead and do it, but if you only have enough to fly coach, don't sweat it.

I've flown to New Zealand in coach, and if you listen to some of the folks here, I should be dead or have lost a limb or something. I got there just fine, and was skiing the next day so obviously, it wasn't that bad.

Having said that, the difference in mileage required to get a business class ticket to New Zealand versus the miles required to get a coach class ticket is a hell of a lot less than the fares would run you. It's 90K miles versus 60K miles, and I guarantee you that the business class fare is a hell of a lot more than 50 percent higher than the coach fare.