Used this on a website for a client that simply wanted to be able to specify when his holiday apartment was available or booked out. This plugin could not be more simple for him.
From my point of view (the developer) it was easy to add into the website's 'Bookings enquiry' page using the straightforward shortcode, and in the main sidebar via the widget.
I'd say it's one of the better looking calendar plugins out there too. Others I've seen aren't quite as tidy.
Highly recommended if you don't need anymore functionality than that. Great support too once we went ahead and purchased the full version.