As much as I like Source, I totally understand to hate it's tools.
Here's a comparision:
While you can do MUCH more with Hammer (Source) as mapper, than with Sandbox (CryEngine 3), it's incredibly hard to make something beautiful.
Let me explain that. In Hammer the maps are made out of "brushes". Brushes are primitive forms (default is a block). Your entire level is made out of those. Then you add props (3d models) for more detail. In the CryEngine those "props" play a much bigger role. They can be much more detailed and flexible. However, you have to be proficient with a 3d modeling program like Blender, 3ds Max, etc. too. As "just a mapper", you can't do as much as in Source.
This is why Source is easy to learn.
On the other hand, Hammer and the complete Source SDK are a pain in the arse to use.
Try to make some natural environment in Source. You'll most likely spend hours and hours of it and it still won't look as good as in the CryEngine, which paints beautiful landscapes as comfortable as with MS Paint.
I can live with it's graphics, but I'd love new tools.
I'd love some real real-time editing too.