Hi Patrick,
I also think EI is pretty good for Architectural Viz. That is what eventually got me into it. You can see some of the stuff I did on my web site (of which much of it was done 7-10 years ago, before GI and all the cool new features… even before ray-tracing).
The reasons, most people have mentioned already… high poly count is huge… quick rendering time… great for HUGE stills… free unlimited render farm, etc. What initially sold me on it was that the UI seemed to make sense to me fairly quickly, and I was able to get better looking renderings out of it without having to get a PhD in its render settings.
I used DXF almost 100% of the time until my modeler, Concepts Unlimited, added FACT export directly. DXF really worked very well for me, and I ran it through a little external utility called Transporter (included with EIAS) to convert to FACT format. Just about everything on my site was done via DXF -> FACT. However, as others also mentioned, lots has changed, so there may be some better formats for you to go from SketchUp to EIAS. But, DXF should certainly work fine if the other formats don’t give you some other advantages (for example, I now go direct FACT rather than DXF because FACT directly supports the polygon normals direction, where Transporter had to ‘guess’ for DXF. Though, I rarely had any problems with DXF… Transporter seemed to guess very well.)
The one possible downside over other apps that I can think of might be EI’s Radiosity implementation if you intend on doing a lot of interior rendering and light studies. The Radiosity is useable, but not quite ‘fully baked’ (pardon the pun). I’d almost go as far to say it has a couple of bugs that can be quite irritating at best to work around (if possible). Now that EIAS has GI, you can probably simulate much interior lighting with it, but its still not a total replacement for Radiosity. That said, there has been some great stuff done with and without Radiosity. I just wouldn’t say that it EI’s strong-point.
Hope that helps,
-Steve