I got 3 550's in use for the past 5 years. They have worked well together and with the following cameras: 20D, 1D Mark 3, 1D Mark 4 and 1Ds Mark 3.
I've also (this year) bought a 5D3 but I have not used the 550s on it yet. For the majority of on camera flash work I've used the 580 II, just because it will seal the connection (weathersealing) with 1D bodies.
If the weathersealing is no issue for you (since you're using a 5D it may not be) then I can recommend the 550s with no hesitation.
Concerning recycle time: I'm sorry, I don't rapid fire flashes. Cannot help you out there. External battery packs will decrease recycle time though.