GWA built your entire website as a Flash SWF file, this can take a long time to load. On one site I visited, the only thing that displayed for the first 10 seconds was a headline and side navigation (in HTML), and I'm on a high-speed connection. When the Flash finally loaded, it loaded a count-down timer to tell me to "please wait" as the Flash page loaded. So they wanted me to wait 10 seconds so that I could see their count-down timer? Wow. In most situations the count-down timer wouldn't have made it to 0 before I'd hit the back button.
Flash is widely supported, many companies still find it difficult to use, and putting your navigation in Flash is just asking to confuse them further. Flash navigation is hard to use because it is not "normal". Most companies are familiar with Web links and buttons as well as the back button. But Flash navigation systems typically use some other method. I have seen sites that completely hide the navigation until your mouse happens to slide over it. Other sites use navigation that isn't standard like photos or even video.
You can set up Flash navigation with links and buttons that look like typical Web page navigation links and buttons, but what is the point? Flash is harder to edit than plain HTML. If you're going to put your navigation in Flash but make it look like HTML, why not just make it easier for everyone and put it in HTML.
Many ads on websites are done with Flash and partially due to how the designers built the Flash, many Flash websites end up looking like an advertisement instead of a place to find information. On one Flash site I visited, the main section of the site is a rotating banner advertising a grand opening, a giveaway of a car, and then finally their company. I nearly scrolled past the rotating banner because I thought it was an ad - but it was the site content!