Once I'm in the gallery, having clicked on a thumb, it navigates fine for me - but I might prefer to have thumbs on buttom. I know you maybe want it in flash, but I'm honestly very happy with ours now being content driven with CMS instead. I also like on ours how I can tell a client to go to a specific one, or I can use a URL to reference to a specific logo. Right now on yours you couldn't do that, and instead if you are on the phone trying to direct them to the 40th logo, it's a little hard for them to find it.
Like you said Joe, you will never please everyone. It's a shame but sometimes you have to design for the lowest common denominator - which is a small business owner, who may not be as into technology as we might like. I think we try to design more assuming that the person navigating is pretty clueless.
By the way, I haven't seen a lot of those logos you posted, but there's some killer work there. Great stuff Joe-