I have an EF-S 60mm that I use for day trips when I don't want to carry an MPE-65mm, an MT-24EX, and spare batteries. But I wanted something better than the flash that's built into my 40D so I picked up a Sunpak Quantary XLF-50 flash. It uses 2 AA batteries and you get about 280 full power pulses out of it with a set of NiMH cells. The hot shoe rolls up into the body of the flash for storage and it sounded like a nice small flash for my day trip bag.
A few days ago I mounted it onto a Kaiser adjustable flash shoe via an off camera cord and connected it to the flash mount that comes with the MT-24EX and stuck it on the end of my MPE-65mm just to see how it would perform. I took some test shots at F11 and ISO 100 all the way out to 3x and the recycle time with a fresh pair of charged batteries was instantaneous. I haven't built any kind of diffuser for it, I just used the flip down diffusion panel that comes with the flash that I don't like (too opaque so I'm sure it's changing the temperature of the light) but the light didn't look too bad! Here's a shot at 1x, F11, and ISO 100:
Here's a similar shot with the MT-24EX:
I made some very minor changes to those images in post, but I didn't change the white balance at all. With a better diffuser I'm sure that the quality of light that's coming out of that little flash will be even better.
The really cool part about the XLF-50, other than it coming in Canon and Nikon versions (E-TTL II, and i-TTL), is the weight -only 7 ounces without batteries. It's so light even with 2 AAs that you could Gaffers tape it to the end of a lens provided you have an off camera cord. The guide number is only 66 but because it's so small and light weight it's easy to get it close to what you are shooting. The sticker shock is $99 USD + the cost of an off camera cord.
Footnote: In some markets the flash is called the Sunpak RD2000.
I've been playing around with the flash today and I've run into an irregularity that has me scratching my head: With the EF-S60mm on my 40D and the Sunpak flash mounted directly to the camera's hot shoe I can get a good exposure at F11, 1/250, and ISO 100 -cool. If I drop the Fstop down to F8, or increase the ISO to 200, I get a black frame. Either of those changes should decrease the amount of light that I need for a good exposure by a full stop and it should be easier for the flash to give me a proper exposure. Turning the flash off and then back on seems to clear the problem. I'll add more to this later as I do some more experimenting. The odd thing is that I didn't run into any issues with the flash connected to an off camera cord when I was testing it with the MPE-65mm...
Update: I connected the flash to an off camera cord and I get the same problem. Turning the flash off and then back on clears it and it starts working properly.