The single rotor unit I built had no static cogging.
The main difference is that I did not have slotted laminates in the stator. It was very similar to the ones Dan built. I think slotted laminates will probably always have some cogging (just physics).

Cogging when producing power I think will always be there, it's the nature of the beast. Besides, it's a good sound when it's humming away. It's power into the batteries and you know it's working.

Regarding alternator built purely from scratch - there seems to be about 3 popular ways of doing things right now.

We can have a single rotor machine, with stationary flat laminates which have the coils glued over the top of the laminates.
 - this may (or may not... hard to say) the easiest way to go.  It works out fine, and the advantages would be the simplicity of it.  It still required a bit of a wide airgap, and I think in the end you need about as much magnet overall as you would if you had a dual rotor machine.  (in other words the magnets would be just as well, or better used in a dual rotor machine)

We can slot the laminates and bury the coils down in them (like any normal "storebought" generator) - or like Ed prefers to do.  I think this must be absolutely the way to get the most bang from your buck in magnets and the best way to squeeze the most power at any given rpm from a given sized machine.  (it can probably be smaller and weigh less)  One drawback might be cogging - depending on how many phases there are and the layout of the stator.

The drawbacks of either of these laminate machines in my opinion are these...

there is a lot of force between the magnets and the laminates, so the bearing is under more stress.  This may or may not be an issue - I think if you use a good tapered wheel bearing it probably doesn't matter too much.  It may make it slightly stiffer to turn.
If you dont use very good, thin laminate material (silicon steel) - then the losses due to both hystoresis and eddy currents will make it stiff to turn, so it will not start as well in low winds and may be less efficient  - especially in low winds.

I built a laminate machine in May (which is currently running at my house).  It has 12 magnets, 1.8" diameter, and 1" thick.  (very large magnets!).  The stator has 9 coils each 65 windings of AWG 14 wire.  Cutin speed is around 150 and it's got a 9' prop on it.  The laminates are behind the coils (almost 5/8" back away from the magnets).  It runs pretty well and I think the output is good, however it is noticably stiffer to turn than a dual rotor machine even though I've used very good laminate material.  For example.. if I give it a good spin by hand...  it won't go around more than a couple times (unloaded).  In this case - it still starts up in 5mph or so.. so it is not a problem - but it's interesting.

The dual rotor machines Ive been making have two rotors - each rotor has 12 magnets 2" dia X 1/2" thick.  (slightly more, but not much more magnet) and the stators are identical (65 turns of AWG 14 wire).  They cutin around 110 rpm.  There is 0 loading on the bearing, and 0 iron losses (because there are no laminates) and if you spin it by hand it turns for a long time before bearing friction finally stops it.  The diff.  in how freely they turn between the laminate machine and the dual rotor machines I've made this year is very noticable.

In other laminate machines Ive made - Ive had problems sometimes with the airgap chagning - the magnets pulling the laminates out... etc, all of which can be solved by better construction.  In the dual rotor machine though its a non-issue.

So, I definitely prefer a dual rotor machine to a laminate machine which has the coils over the tops of the laminates - it uses about the same amount of magnets to get the same output, and it turns more easily (starts turning in lower winds) and is probably a bit more efficient.