has anyone used an AKG Solid Tube microphone? I've been offered one for 600 Euro and I'd be grateful for any comments or opinions on this mic.

I didn't like it, but that's just my opinion. For less money and a similar type of mic I prefered the Red5 audio valve mic.

http://www.akg.com/site/products/powerslav...anguage,EN.html

a nice Vacuum tube large-diaphragm microphone
You gotta hear it to love it, don't listen what people say , ley your ears dicide what they like ,if it is good for your kind of applications go for it.
I think this is a great vocal condensor .