I have one
I have a Cool-er and I am very happy with mine. I pre-ordered mine and got it in July. I admit that orignally the firmware was having issues and mine had to be replaced, but Interead got an A+ on support and replacement of the device.
I have a newer version of the firmware but not the newest. The device is very stable, I have only had one hard crash on it where I had to reset the device, but normally it works fine. I am a very heavy reader and normally going through 3+ books a week.
I use Calibre with my Cool-er and it works very well.
The change they recently had with the newest firmware means that it no longer opens up to the page you were on. When you open the book again it will go right to the page, but not when you intially turn on the device. The speculation on the reason for this is to help prevent loops if the ebook you read has a corrupted file.
I do not buy my books from Cool-er's bookstore, so I am not sure on the formatting quality. There are tons of free books through Project Gutenberg, this is stuff that is public domain.
I buy most of my books through Fictionwise and Books on Board. I like that the Cool-er supports Adobe's secure epub format.
I am happy with my Cool-er. The page turning button could be better but I hardly notice the hard plastic around it anymore. The button its self is not hard to press, it is simply flush with the cover, this means that when you press it you generally have half of your finger also pressing on the plastic which is very firm. This has lead people to say that the button is hard to push, which is not entirely accurate.
There have been complaints that it feels "cheap". I think that is because it is made out of a very lightweight plastic. I don't feel like its cheap or flimsy, though its not as durable as my EB1150.
Hope this helps!