It's the only option I currently have available for paying eBay purchases, even though I have a confirmed bank account and have made instant transfers in the past. I sent them a message asking about it and they say I have to have a credit card on file now to make instant transfers. I'm not keen on giving them my credit card number so I haven't done it yet....
...The last payment I made was withdrawn from my bank account the day I made it but didn't get to the seller until 3 days later (that's when I received his payment confirmation). This is sleazy on Paypal's part, because they make their money on the interest they get for funds held in their accounts; by adding a built-in waiting period for these echecks they effectively get a lot more money... not to mention making sellers wait for funds and buyers wait even longer for their purchases.
I'm very disappointed with Paypal over this.