Dev textures are just plain easy to keep yourself to the correct proportions of a map. But it's also something handy when you have to scrap a whole piece of the map in its design phase. If something doesn't work in terms of gameplay, it just doesn't work.
At such a point, the dev textures allow you to just change that piece of the puzzle, without having to worry about anything such as textures and what have you.
There's a good ratio between people constructing their map in the nodraw texture, and in the developer orange maps. Personally, I would just go with the dev textures. In the end, you can still let Hammer replace any developer texture with nodraw.
But as stated previously, any level designer should just stick with what feels most comfortable for him or her.
On behalf of the map, I would say it's making progress. Although that we as viewer can't really give you that much feedback on a map in it's very early phase. Try to keep some variety in your texture work, don't overuse.




