Uses for which I need a second cheapish flash: backup to my 580EX, use by a second at events, use in a dual umbrella setup.

If you have used this flash, I would appreciate any input. It seems like a good deal at $138 shipped. But I am worried: will it be powerful enough to help light a group? Any known lag or other issues using radio triggers? How is the manual functionality? Thanks a lot.

Never mind. It has almost no manual functionality to speak of. Looks like I will be picking a Bower or other unit.

No infra=wirelss master/slave control with the 580EX.Slower recharging times.Poor building quality(not that the 580 is good as the SB800).ETTL not as good as the 580EX.
If you are looking into a second flash with less cost,go for the 430EX:can be a slave for your 580 and is not as bulkier as the Sigma flash...

PEACE

I already have radio triggers on the way, and don't plan to use optical slave mode on any flash I buy. The 430EX is nice (I used to have a 420EX and liked it plenty), but if I can get a flash for half the money that offers more power and meets my needs, I will.

A note about recycle times: if you use very little flash to begin with, as I do, many flashes would fit the bill for most single-flash event uses. When posing groups, recycle time should not matter as much. Reliability and maximum power of course always matter, and fast recycle times are always desirable.

The 430EX has a guide number of 141' / 43m @ 105mm. Some of the third-party flashes I'm considering now:

Bower SFD926C: E-TTL, wide-angle diffuser panel, GN 125' / 38 m @ 85mm, $110

Nissin Di622: E-TTL II, GN 144' / 44m @ 105mm, 6 power levels down to 1/32nd, $150 (I figure I have liked their Ramen noodles in the past, why not try the flash?)

Vivitar DF 383: E-TTL, GN 148' / 45m @ 85mm, 5 manual power levels down to 1/16th, $130

Looks like it will have to be the Vivitar, unless I score a great deal on a used 550EX, 580EX, or 430EX soon.