1. Extrude Text: if you use Dtext (single line text) with an AutoCAD Font (like Romans, not like Arial), you can use command-line CHPROP to change the Height property of the text. It's not actually like "extruding" but it works fine. Another way is to use express tools to explode text and then extrude polylines. You must have Explode Text in Express menu to do this.
2. Transparency: If transparency is set to 1.0 the solids are simply invisible. I didn't understand what's the problem. I've never noticed it.
3. Circular stairs: I don't remember exactly Architectural Desktop 3.3 but there's a way to trim the stair edges with a polyline. It could help you. What kind of circular stairs do you draw?
4. ArchiCAD vs Architectural: Sorry, I've never used Archicad. What I can say is: Architectural is very flexible and configurable. Even too much, as it can be really hard to draw non standard things. But it is finally AutoCAD with addons, so you can use AutoCAD features when it's getting too difficult to obtain something in Architectural. I think Archicad isn't so flexible. I don't know
Sorry for my bad english and bye
