Not saying that it shouldn't be part of standard AC, but the CadImage Accessory Pack does this pretty well. Fascias, spouting, valleys, hips, downpipes, roof surface, soffits, etc., not to mention wall profiles and claddings(may be redundant in 10?), slab extras (footings etc).
It is not associative, but you can do continuous slab edges and footings pretty easily with Complex Profiles now. If you want it to be associative, you can use the Railing Tool in AC21 / 22, though that is a little bit more complex. The railing tool in regards to roof fascias was discussed over here.
Stephen, I started messing around with the new railing tool as suggested by Lingwisyer with almost satisfactory results. The big plus is that it is associative.
A few of the negatives are that you can't define rail profiles by segment (at least I haven't found a way to do so), so the corners don't connect if you have intersecting profiles that are different. The fills don't appear to behave the same way as they do in a wall that is a complex profile, in the project, I am working on they are coming in on at a different scale, and the profile is merging like items that are touching, whereas in a wall they no longer merge together.
At the end of the day, I can get the visual results I am looking for, for the most part anyway, and the information I need for material takeoffs is available. I just think that there could be improvements.
Jason wrote: you can't define rail profiles by segment
In edit mode, you can select the rail, or any other element, within each segment and change the profile. The downside here is that once you have modified as segment in this way, it will no longer respond to general changes made to the overall railing.