You don't need to worry about the keyboard cover scratching your iPad, as rubber bumpers at the keyboard's corners prevent contact with the screen when it's used as a cover. It's not a Smart Cover replacement, though; the Keyboard Cover is thin, but it's not that thin.
The Ultrathin Keyboard Cover also doesn't , or its sides for that matter, hence the term "cover" rather than "case." I found that the third-gen iPad had to be used naked with the keyboard in order to fit in the groove, but the iPad 2 worked with a Belkin Snap Shield attached.
The Bluetooth keyboard has an internal battery that charges via an included Micro-USB cable. Logitech claims the keyboard will work for six months between charges if it's used for 2 hours a day. I had no way of getting close to proving that claim, but the keyboard paired easily enough via a standard PIN-based entry. Once it's paired, all you'll need to do is flip a side power switch on the keyboard cover the next time.
This plastic-and-aluminum accessory marvel is pricey at $99, but it really works...and it's surprisingly comfortable to use. The raised keys have solid travel and don't feel mushy. The Delete, Return, Tab, and Function keys are cramped on the sides, but the main QWERTY keys are close to what you'd find on a Netbook. There isn't much of a raised surface, so the keys ride close to the level of a desk (that could aggravate some people from an ergonomic perspective), but the Keyboard Cover makes the most of its space limitations, and offers unobstructed access to the keys (unlike the original Zagg case, which had little walls on the side of the keyboard).
Dedicated iPad-oriented controls are layered on top of the number keys and are Function-activated. Cut, paste, volume control, play/pause, and some rudimentary cursor controls are included, but none helps with the iPad's chief limitation when keyboarded, which is that there's no mouse or touch pad control.
I wrote this whole review on the Logitech Ultrathin Keyboard Case, and by the time I finished I found I'd adjusted completely to the keyboard. It's not a true full-size keyboard like the, but it's more easily portable. It's the best ultraportable keyboard I've seen for the iPad, and it's smartly designed. Just make sure you have a good soft carrying case or an easily removed back cover when traveling.