I've had my 30L for about a ear now. It is by far my favorite fermentor. I've only once experienced the need for a blowoff, but that was no biggie. If you look around you can find where people have modded them for thermowells and using them for push transfers with CO2. They aren't transparent but are translucent so you can still tell some things about your fermentations. I currently use mine in. 5.0cf chest freezer and it fits fine.
Oh and the white caps that co on your carboy hood? They work as a perfect cap for the spigot.