Compared to Canon's 430EX II
- Better price (~8k php vs ~14.5k php, ~12.5k php respectively)
- Higher guide number (32 vs 31, 30 respectively)
Also has TTL for the "automatic" shooting needs, and pretty much all of the features that can be found with the OEM flashes.
For photography enthusiasts, based on the specs, the price, and the reviews I've read, I highly recommend this flash.
I'm getting one soon, hopefully, to complement my 580EX II