No thanks. Like many, I've already got all my eggs in one basket by using a password manager where everything is stored in the cloud. No way I'm going to double my risk of exposure by putting all my financial accounts in another online account. Besides, keeping track of my half dozen or so financial accounts is easy and doesn't warrant the use of something like Mint.
I wish banks would allow you to create read-only accounts. Then, I'd happily use such a service.