Hmmm...the guy who said the doom3 editor is just a speeded up Qradiant...where do you get your info? Or was it (partially) included in that alpha leak? I haven't heard much about the level editor, so I'm curious where you get your info from.
As for making levels: if you've never done it before (making levels or any other 3d work), it's hard. Screw the guys who say 'making 'em is easy, making good ones is hard'; somewhere they have a point, but the fact is that starting out in anything 3d (modeling or level builing) is fucking hard, unenjoyable and frustrating. When you know about vertexes, edges, polygons, turning edges, splitting edges and polycount it becomes interesting, and then it takes a while before it actually becomes enjoyable. And after that it takes a while before you can actually make something that is worthwhile/good. Then it becomes great fun
So, to recap: it's one of those things which take a long while to get into, but once you're there, the rewards are great (just make sure that when you reach a point somewhere in that neighbourhood that you use a spam-mail account in your readme's :)).