Has anyone tried this accessory?

[yoitsnico]

Has anyone tried to use this?

Sprint HTC Hero Sync and Charge Desktop Charger with 2nd Battery Slot

What are the pros and cons to it? Is it worth buying? I'm really interested in a product similar to this.

Thanks.

 

[TheBiles]

Here's a big con (for me at least): You have to take the phone out of the case (assuming you use one) to use it.