I start to get the whole concept 😉 First i was not too overwhelmed with the new Gumbo stuff. Drawing with mxml did not looked too appealing – but it totally makes sense. By seperating the skin from the actual component in a clean way with it`s own format (fxg) it will be very easy to build a great toolset for the designer <-> developer workflow.

You can get a first impression if you check out the Fireworks beta on adobe labs. It has an export script that generates fxg out of your vector drawing – very cool! 
I think Fxg is really the missing link between designers and developers and it seems once again Adobe is getting it right. Ultimately Adobe will use this in Thermo and I think that Fireworks 10 will only get limited support for fxg. Maybe it will just be this little export snippet.

This is where i`m not so sure. I think the hardest part in getting developers and designers work together are the designers tools. From my experience it`s very hard if not impossible to make a designer switch to a new tool. They love their Photoshop and maybe a little fireworks for web stuff. 

But getting them to use a new tool like Thermo can be hard. Just look at Expression Blend from Mircosoft. I don`t really see designers using this tool and if – they are forced to do so 😉 So maybe it would be a better strategy to include the Thermo stuff into Photoshop or Fireworks. Or make it integrate so super smooth that they don`t realize that they are using a different tool. You have to trick them Maybe even call it “Photoshop Interactive Designer” (Na that does not sound Adobeish).
Anyway some interesting links to get started with fxg:

Get Gumbo (Flex 4 SDK)

Skinning A Button in Flex 4 Using FXG

Jumping Into Skinning with Flex 4

Gumbo (Flex 4) Skin with Transitions

 Flex 4: Neue Grafik-Library (German)

Fireworks 10 Beta (2 day trial – more if you`ve a FW9 serial)

Man can`t wait till I can use this in production 😉