I can't underestimate the time and effort QuArK saved us in the process. We have many people in the lab, with a wide range of programming abilities, but everyone is able to learn the basics of how QuArK words and design their own custom experiments in a matter of weeks without much training. In fact, the environment used most extensively used in the paper was conceived over lunch, and implemented that same afternoon. A testament to how easy QuArK is to use.

Source: Forum

Before I became a developer for QuArK, I used QuArK to teach myself the art of making maps. I chose QuArK because it was much easier to learn than the other editors for Quake 3, and because QuArK supported so many different games.

Source: Conversation

Two things made me give up with radiant and go quark for my OA map.

1st. It's impossible to make hollowed 16 sided cylinders (not bezier curves) and cones. I always notice microgaps because perfect, regular, polygons have non integer vertexes coordinates.

2nd. For some odd bug radiant is refusing to save maps unless I use a different name, else it does nothing. That was caused by light entities having intensity values too large, or something else related to lights, after I deleted all lights my map saved just fine No, it's something related to entities in general, not just lights. Or... some shader.

Source: Forum

First of all, I would like to say GREAT WEBSITE!

This place will help me out tremendously on what I need to accomplish...and thank you to the developers of Quark, my hat goes off to you.
I will probably be frequenting these forums a bit.

Source: Forum

I just have to say wow. Kudos to you guys for developing an awesome editor. This is just miles and miles above the experience I've had with gtk/qeradiant. Somehow I had never heard of QuArK until yesterday, and I've spent some time researching Quake 3 editors and talking with Quake 3 mappers in the past. I'm looking forward to using this tool once I get some inspiration.

Thanks so much for the development effort! I hope you keep it up and this tool becomes THE existing-gen (no idea what's in the future with Idtech5, but it sounded like significant changes to level development) Quake engine map editor.

Source: Forum

QuArK has got very precise and easy texture and brush manipulation (floating points), a very fast 3D window, integrated programs for pak viewing (including .bsp decompiler) and an easy to customise interface.

Source: GameDesign.net Forums