There's a couple ways to look at this. Make sure that the 1,000 miles per month has no caps and no end date and comes every month. Usually similar offers have caps on the number of miles you can earn.

As mentioned, there's a coupdl ways to look at this - and others will add. First of all it's a $12 monthly difference. If you kept this up for 20 months, you'd be 20,000 miles richer and at the special award level that Citibank has for various AAdvantage awards. Now, based on your currect ISP, that means you'll have spent $240 more than you would have if you had not changed ISPs. Bottom line for you - do you see the use of this free award from Citibank/AT&T as having more worth than $240? Would you have diligently saved $12 a month toward your next vacation trip costs? Do you see this as a 'Christmas Club' for free travel? Only you can answer these questions, but for most people - I included - I'd say it's a fairly good offer because as other will note for you - you're buying miles at 1.2 cents per mile. Pretty good for this situation.