I am currently designing and building a village in the Skyrim Creation Kit. Doing that, I am working with landscape in vanilla Skyrim worldspace, I am creating both interiors and exteriors and I am making NPC's come to life. So far, I've done all of this, but my mod is still Beta and cannot move beyond that stage until Bethesda fixes some bugs with the CK that prevent effective enjoyment of the mod for the player.

The following three bugs are therefore on my priority list of what I'd like Bethesda to fix as soon as possible. In order:

1. The NavMesh Bug. This bug is most serious and needs Bethesda's full attention. Upon entering my village for the second time after having been away adventuring elsewhere in Tamriel, the player will note that all my NPC's will behave weirdly. Some NPC's will jump up and down through the floor and some will wander about instrange locations.

2. The Grey-Face bug. This bug makes my NPC's look ridiculous in some cases and therefore makes my whole mod seem unfinished until Bethesda addresses it.

3. The Floating Grass bug. This bug strikes some players, but not all. I've not experienced any sort of flying grass in-game myself. The bug has a http://frontierskyrim.wordpress.com/2012/02/28/floating-grass-in-primby/ though, but it would be nice if Bethesda got rid of the bug.

Bethesda has confirmed that they're working on those top-two bugs in my list, and that's the only reason I keep building my village. If I didn't know there was a light at the end of the tunnel and that the NavMesh and Grey-faces will be addressed, I would not be modding Skyrim right now.

I think all mod makers agree the first to need addressing urgently they break most mods

I've experienced all these bugs, the flying grass is very distant for me in the CK, I don't see it in game.