@willis : I agree that they should keep one electronic shutter model in the line up. even if its down at the D40 level.. The other advantage of the electronic shutter is that the 1/8000 is a true 1/8000 second capture of the full frame. where as the FP version of the 1/8000 is not as it still takes the shutter 1/250 of a second to travel from top to bottom. so if you take a picture of a vertical object traveling from left to right it will look skewed or slanted just like when you swing a ruler in front of a TV screen.

Unfortunately Auto FP is not something available on lower cost cameras.
D40 has an electronic assisted shutter, something that CCD sensors had, that has many drawbacks, but one advantage is higher flash sync speed. I do not think any newer CMOS based DSLR camera has it.
And yes you could use ordinary light sources as a fill-in if you have time, skill and will to do it. For example you could build a macro set that uses 2 or 3 fluorescent ring lights and stand for your camera from an old enlarger for a fraction of price of Nikon R1 kits and get much better results overall.

Willis:
Re shutter speed, I used to think it was a hinderance, but with Auto FP High speed sync I can still get great results all the way up to 1/8000 sec. I know it drains battery and power, but its not as handcuffing as people seem to think.

NikonUser... love the ikia lamp idea. Much cheaper than a nikkon strobe.

Dash - I think the 600's are great for CLS... probably all you need. The only advantage to having more power is that you can position your light further away, which can be important. Especially if you are using modifiers (umbrella, softbox, whatever).

NSX: The D40's better flash sync speed is due to its electronic shutter. Technically, you can sync it as fast as you want, but Nikon caps it at 1/500th. There are other advantages (I forget what they are) to a mechanical shutter, which is why Nikon uses them on their pro bodies. They should, IMO, keep at least one electric shutter model in the lineup.

I love 600's! I do so much CLS and ive got 3 now, and when they come up on CL I do everything I can to grab em. People say they are not powerful enough, but Ive yet to be standing there thinkin I need more juice. My 800/600 combos work just fine for me.

it really depends on a lot of other considerations as well. personally, i have more than a dozen sb-600/800/900s for my professional work. but on the other hand, in a small indoor environment, i would use no more than two strobes most of the time.

here take a look at an example.

http://farm4.static.flickr.com/3642/3393685060_d3a4ef082d.jpg

Camera: D700
Lens: Nikkor AF 35mm f/2D
Manual Exposure 1/60th f/2
ISO 200
SB-600 Bounce flash +0.7EV 90 degree to the left wall

on the back of the subject i used a $4.99 IKEA table lamp (7-watt) to get rid of shadows.

It's really odd that only the D40 has the 1/500th sync speed. How come the more expensive DLSRs can't keep up with the entry level baby?

The only advice I can add is that if time is no object then wait a while longer. The SB700, if the rumors are true, could come out any second now. That usually means that stores want to get rid of the SB600 fast, so you'll get a good deal. Or that's what I'm hoping for, anyway, since I want a SB600 too.

Thanks MB. I wound up with all this flash kind of by accident. I bought the SB-600 for my girlfriend to use for her event photography. The problem is that alot of her stuff is shot in larger banquet halls. So for the primary flash, you really need something more powerful or you wind up with blacked out ceilings. So eventually we upgraded to the SB-800... Three days later the released the 900.

User friendliness, when it comes to flash, can't be understated. Nikon cracks me up because their cameras are such a joy to hold \ use. But the ergonomic prowess starts and stops w/ their SLR's. The flashes are possibly the most counterintuitive hardware that I own. If it weren't for the good folks at Strobist.com, I never would have discovered all the other cool functionality they built in.

It was ages before I found out I could turn the flash off all together and just use the much better "Red Cross" auto focus assist for low light shooting. It is much more effective than the annoying light on the front of my camera. Good luck figuring out how to do that from the manual (OK, I'll be honest. I didn't go more than a few pages into the manual so its probably in there... I just can't understand the darn thing).

Once you learn what you are doing, its not as bad. But if you just pick up a flash and try to start using it... good luck. I can't help but wonder how many features are in there that I still haven't discovered.

Wow, you have really invested in your flashes.
If you only need additional fill-in flash SB-600 is probably the best choice, I doubt that even new SB-700 will have any advantages there.
If you are planning to go for FX, than SD-900 could have some sense, but otherwise it is not really that better than SB-800 except in user friendliness.

So I think I'm going to pull the trigger on a new flash. But I"m having trouble decideing between a second SB-600 or a SB-900. With my current setup, I've got a SB-800, and a SB 600. Usually when I'm doing multi-lighting set-ups, I leave one flash on camera dialed down a bit for fill, and a second flash at a 45 degree angle (or whatever looks best) at full power for my main light source.

I've just gotten started with this look, and quite like it, but I find I'm getting some pretty harsh shadows if I have a backdrop close to my subject. I'm thinking putting a third light behind the subject might help balance things out just a bit.

I could, of course, just use the pop-up for fill, and put the SB-800 somewhere else, but that limits me to the D80\D90, and I really like using my D40 because 1. I don't have to ask permission from the mrs. to use it, and 2. It will sync up to 1/500th of a second, which gives me more control over the ambient light.

I suspect an additional SB-600 is all I need for the above, but I was wondering if any of you 900 owners think it would be worth the extra money (another $250) for the additional brightness and gadgetry offered by the 900.