Does Earthlink have a good reputation for actually posting miles/credits correctly and promptly? If you will have to make phone calls, wait on hold, write emails, etc. to eventually get your 4 credits or 5000 miles down the road, it makes those rewards worth significantly less because you have to invest your time to get them.

I assume the $84 is just a billing credit. Figure there's at least a 50% chance they'll get that right the first time. If they hose it up...well, they can fix billing credits pretty easily with one phone call.

Remember: telecommunications companies are NOT to be trusted. Take the quick reward - the one you know they can't blame on another company if it goes awry.