Solids, whilst they can be used on their own to create decent structures, are also very useful to be used as placeholders, and then exported to 3DS Max. Using this placeholder you can then create an accurately scaled model easier.
No doubt CryEngine2 allows you to have some fantastic water but not everyone wants a map with an island setting or an abundance of water. Find out how to rid your map of it!
CryEngine2 and Sandbox 2 allow you to seamlessly view your created world from a variety of angles, just as easy (possibly even easier) as you would when actually playing the game.