Just be thankful that they are notifying you!! By federal law, they are required to inform you if you're information is "compromised." I've been in this situation myself in the last year and it is a sickening feeling to know you're about to tell thousands of people "your information has been compromised." However, it's better than the alternative. At least you have the opportunity to PREVENT identity theft which is much better than trying to RECOVER from it!! It took me three years and the help of Clark Howard to straighten out the mess a check-out clerk at Walmart created in the mid-90's by using the info on my check to get a job and buy a car!
I am actually surprised that they are paying for credit monitoring! That's a big plus for them!!
Anyone that gets the letter should take them up on the offer. If you do not, you've relieved them of all obligation to help you rectify the situation if someone does choose to use your SSN or DL.