One of PayPal's and the Banks' most popular products is "repeat billing" or "subscription payments".
Customers love it for it's ease of use and businesses love it for the constant income.
I should be able to enter a bitcoin address into my bitcoin client and pay it the exact same amount of bitcoins whenever I so choose.
Imagine having all of your subscription payments easily accessible from a single program on your desktop?
Right now I have to make sure I top up my cell phone every month with my credit card through their website. I have an automatic payment setup to withdraw money from my bank account for a dedicated server I rent. I have care insurance payments that can only be dealt with via fax+phone being charged to by checking account. And I have some forum subscription payments that go through PayPal. It's a nightmare to change any of them. If I could just click "cancel subscription" or uncheck a box on my desktop to cancel a subscription I would be thrilled!!!
It's a good idea, but probably not a deal breaker right now. There are lower hanging fruit to go after. At least in my opinion.
Sure, not a deal breaker. But it's a pretty simple implementation (windows already has scheduled tasks, and linux cronjobs) for a major improvement in the client imho.