Funny you should ask about this -- have just been trying out Silhouette this week at work.
It's a wee bit pricy but there's a fully-functional time-limited demo to download and play with... a colleague of mine tested the stand-alone app while I messed with the Illustrator CS plug-in. Both of us agreed that the plug-in was much better.
From my limited experience of it, it seems to be quite good but I haven't sent anything to press with it or even run any of the eps's through FlightCheck. Some of the eps's gave the vanilla office laser printers a headache when embedded into PDFs but I suspect that may have had something to do with the RAM in those printers... they ripped fine on our proofer.
Anyway, have a play. See what you think... the tricky bit is messing with the settings to get the exact result you need. The B&W line results can be quite beautiful...
They abandoned Dimensions to, which was a limited, but extremely useful object 3D orientated environment program. I would say they have not seen customer numbers worthy of updating it. However, much as they integrated a hopeless imitation of Dimensions into Illustrator CS as a effects plug-in, I'm sure I heard the same rumoured for Streamline in the next release of Illustrator. Let's hope they do a better job than with dimensions. BTW I still use both under Classic, just fine.