Ken Rockwell, a reliable and "to the point" photo blogger, started a writeup on this flash unit, but the last time I checked, it was still under construction. He did make some wonderful photos of the unit, which I'm including here, along with links to his article. Granted, I can see why this flash wouldn't be Priority One on his, or anyone's, blogging to-do list, but having purchased one and played with it a fair amount, I can think of a number of uses for it. Incidentally, for a posting from DPreview, click here.
The unit uses a single CR-123 battery, which contributes to its small size and rapid recycle time. However, the batteries are expensive when compared to AA cells. It does not offer iTTL metering as does the Nikon SB-400, my other tiny flash. But it offers far more exposure control features than you might expect. For starters:
Non TTL Flash Exposure Metering: The unit has its own sensor that meters out four measured bursts of light that will provide proper exposure for four basic aperture settings at ISO 100 and four more at ISO 400. Need something in between? You can easily extrapolate what you need for ISO 200, and maybe even ISO 800. While a full post on non-TTL flash automation is justified, it suffices to say that for fill purposes, the SB-30's non-TTL metering mode should work well, or well enough.
+/- 1/2 Stop Exposure Compensation: This is an interesting tweak, but rather limited.
3 Manual Output Levels: You can set the flash to manually discharge a "full" discharge, plus 1/8 and 1/32 power discharges. This could be very handy in situations where a precise (and small) burst of light is all that's needed.
Built-In IR Panel: Like the Nikon SB-50 DX, there is an infra-red panel you can use to cover the flash tube for use as a wireless optical trigger. Unlike the SB-50, there is some white lite leakage, a definite distraction when photographing anything with functional eyes.
SU-4 Style Optical Slave Modes: The orange M and A allow for firing the unit as a optical slave, but only at full power in the M(anual) mode. Haven't quite figured out the A(uto) mode, but just having the slave feature is cool enough.
So where does this unit fit in? First off, it's small size (it could probably fit in a cigarette box) makes it a great fill light for a compact camera that can take advantage of the speedlight's manual controls. Used in either the non-TTL or the manual mode, you can arrange for a fast fill light solution, or a more precise flick of fill light, depending on what you need. It sits very close to the lens axis, but not close enough to cast a shadow when your wide angle sports a petal lens hood.
I'm pretty impressed with the flash, and plan to use it for filling some upcoming outdoor events. We'll find out whether I picked a winner or a loser!
*Micro is my descriptor. When compared to the SB-910, it is REALLY small!
February 10 Addendum: I used the flash with the IR Panel in place to trigger a wall-bounced SB-800 in SU-4 Mode. Using a 60mm 2.4 Macro on a Fuji X-E1, I made this selfie (Photo #1):
Incidentally, the shot is full width, with the cropping affecting only the top and bottom edges.