It will work but not have all the fully automatic modes available for that on digital you need one of the EX flashes such as the 580. If your looking at flashes I'd urge you to consider sigmas models as they are well specced and very competitively priced.
is the 550EX better than the 430EXII?
I bought one of the Jessops £35 bargain flashes, works fine on my 5D,
I suppose it depends on the use it'll get, I don't use a flash very often so a bit of bounce and the ability to alter the angle is all I need so it does for me.
I suspect it'd also be OK for a lot of users but they're suckered in by shiny kit syndrome and buy a top of the range flash with features they'll never use