Should I upgrade from the 7D to 5D mark 2 upgrade.

I would have thought that you'd pick the 5DMKII to begin with. I'd imagine that you work frequently in low light situations and the 5D beats the 7D any time in that department. I can't imagine that you really need the advantages the 7D has over the 5D - continuous shooting, more and better AF zones, etc. If I were in your shoes I would indeed upgrade to the 5D - IQ will be noticeably better.

Is that you yahoo Dang?
If you've already got the 7D you are going to chuck away a lot of money by going to a 5D.
For band photography the extra reach the 1.6x crop gives will be handy.
An effective 80mm f1.8 for the price of a 50 f1.8?
An effective 160mm f2 or 320mm f2.8 for the price of a 100mm f2 or 200 f2.8?
There is a lot to be said for cropped sensors.
The low light performance on the 5D2 is a benefit, but only a massive benefit after ISO 1600.
With a flash and/or fast lens I'd hope to be more in the ISO 400 or at a push ISO 800 range. Remember (because most folk forget) you shoot for the lit areas with concert photography, not the black areas where you will never record any detail.
A 7D will give photo quality at A2. How much bigger do you need to go at photo quality, an extra 3MP will not make any meaningful difference at these kind of sizes.
The 7D has an AF system that dances all over the 5D2s, as does the frame rate.
If the previous poster doesn't see a need for this in band photography then they haven't done it.

My only disagreement with the previous response is with the benefit of the cropped sensor. I haven't used both cameras side by side, but I strongly suspect that 5D2 images will have significantly less noise at high ISOs than the 7D, even after you crop the full frame image in your computer to be the same size as what you would get from your 7D. Even though you will end up with a bit less resolution with the 5D2 after cropping, I strongly suspect that the IQ of the 5D2 will be superior at high ISOs. And if you want shallower depth of field, that will be easier to achieve on the 5D2 as well.
I don't know what your shooting habits are or how large you want to print photos. I've shot a few concerts with my 40D, and I didn't like using my flash at all. I much preferred the stage lighting. So I ended up shooting at ISO 400 - 1600. This worked well for me, and I did get usable images, but I imagine I could print them much larger with a 5D2. If you're happy with the noise levels on your 7D now, I'd suspect that there's little reason to spend all that money to upgrade. If your clients want prints larger than what the 7D can handle, then by all means upgrade. Someone with more experience with both cameras than I could say for sure, but with a 5D2 you may be able to increase the size of your prints by 50% or more. If you can, borrow a friend's 5D2 and compare.

Are you sure that is an upgrade? That depends on what your needs are.
The 5D2 is a very nice camera if full frame is want you need for your shooting. However the focusing system is nothing to get excited about.
I would choose the 7D for the benefit of the cropped sensor in nature photography. Also the 7D has a much better focusing system that is very beneficial for nature and sports photography.

I own both and prefer the 5D2 for concert photography because of it's much better noise performance at ISO 1600 and 3200. At high ISO and cropping it's clearly better and easier to work with. Still, a question would be which lenses do you have and do you have stage access. A 70-200mm covers a lot of ground on the 7D, but your may feel out of reach, unless you're on the stage or right in front.

Both camera bodies are quite workable, but the sharpness of the 5D2 when used with superior lenses is really hard to beat.

If these are events in which beer gets thrown around the 7D is better sealed...

I got beer on both my 5DII and 7D and they did fine. Either camera is great choice for stage photography: 7D has an advantage in off-center AF whereas the 5DII trumps it at ISO above 800.

I love the 5D2 for band photography but I would think a 7D with the right lenses would do well too. What lenses do you use? I find the 85 1.8 works well as does the 70-200 2.8.

The print size limit is about the same for the 7D and 5D2 at low to mid ISO. At high ISO 7D print size is bound by noise, and the 5D2 can therefore print larger. So you have to ask yourself: how important is it to be able to shoot at, say, ISO 3200 and 6400 yet be able to print larger than an 8x10 or 11x14? If it's very important, 5D2. Otherwise, save your money.

Other than that the only real 5D2 advantage in my book is the ability to use certain lenses (or rather, use them at their intended focal lengths) such as the T/S lenses. That's not an issue for what you're doing.

The DoF issue is always raised, but it's actually a non-issue. Fast primes will blur the background on both 35mm and APS-C. The difference in blurring between these two formats is equal to maybe a one stop aperture change. You could blur the background more by spending the $1,000 difference on one or more fast lenses.