Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: What Pro-Level Flash for my Canon 5D Mark II ? Which of the Canon Speedlites are compatible with the 5D MkII?
Document: I have had this unit over a year now and it works great with both the 5D and 5D Mark II cameras. The flash has been highly reliable and I have had no problems at with it. It is a definite improvement over any other Canon flash unit ever made.
Bought this unit and used it for on my Canon 5D Mark II and 5d Mark III. After about 1 1/2 years of light usage (I do not do a lot of flash photography), it quit working. Even when it was working, it did not function up to my expectations (I do know how to use a flash and what it is suppose to do!) The overpriced repairs by Canon cost me around $200 (minimum charge).
I bought this unit for my Canon 5D Mark II over a year ago. I what I like about this unit over the Canon 430 EX is that it's able to detach from the shoe very easily. I will admit in my over zealousment that I may have screwed it on a little too tightly but the 580 EX II is a no brainer when it comes to attaching and detaching the flash unit. As far as performance... no problems and if any glitches did occur has been user error.
I own a Canon 20D (Waiting for the 5D Mark II If it ever comes out). My main walk around lens is the Canon EF 24-105mm f/4 L IS USM Lens as well as the Canon EF 70-200mm f/2.8L IS USM Lens. I previously owned the Canon Speedlite 430 EX. I recently purchased the 580 EX II.The 580 EX II is very powerful so I recommend a diffuser. Your pictures can come out looking very  harsh if you're not careful.
The 580's AF Assist Beam is aligned with the focus points on all Canon EOS bodies.17  Master/SlaveThe 580 can control (master) and be controlled by (slave) compatible Canon Speedlites, as well as the Canon ST-E2 Wireless Transmitter, for a very portable and flexible lighting system. The 580 can control up to three slaves. The Flash compensation and the ratio of each slave, to the master are all programmable by the 580 with wireless communication for the `network'.
It syncs with high speed Canon shutter speeds, has automatic or manual matching of the unit's color temperature output to the camera's white balance setting, and full integration with  the Canon 40D, 50D, 1D MkIII and, I believe, the new 5D MkII. I control my master 580EX II unit directly from the menu of my Canon 40D camera. The master unit can be set to not fire with the other flashes and still  send out the pre-flashes to control all of the slaved strobes.
For my amateur purposes, it was overkill. I just needed a flash that takes excellent pics and has great features. I suspect that for most people who want to just take great shots, the 430 would suffice.So why the 5 five stars? Because objectively speaking, it is an excellent, powerful flash with pro-level features. If I had a better camera, I would buy this again.
In other words, you don't need to pair it to a 5D or a 1D Mark III to notice how much better than the 420EX it performs.
I find the best way of getting it back to single flash mode is to open the battery compartment while the flash is on. This factory resets the flash. I believe another way is to push the reset button on a compatible Canon EOS camera.Oh yes, as with the 550ex I find I have to increase flash exposure by +1 stop with the 580ex II. I don't consider this a fault of the flash, just my preference.
I own the 580EX and ordered the 580 EX II because of its electronic compatibility with the new EOS 1D Mark III (which I have on preorder). The new coupling mechanism is a blessing, not to mention the wireless capability if you're so inclined. Another great Canon product. If you need a professional flash unit, and can afford it, put this one on your shopping list.
Answer: If you have made the investment in a 5D MkII I would suggest adding the 580EX II to the equation. In all honesty I would look at getting 2 580s which would give you a mobile studio. In terms of compatability, any of the Canon speedlites will work. The 580 delivers the most power which is important because more power =more flexibility. I hear people say the 430 delivers enough power to light anything in any situation. This is true, but you often have to run that 430 at 1/1 power where the 580 would be at 1/2 power, meaning faster recycle and 2x more pops per battery charge. The 580 is also the only Canon Speedlite that has a PC cable connector. Trust me - that is a big deal. I use 2 580s and I can shoot almost any situation without being tied to a studio.