I don't think using Silverlight excludes showing panos in the usual small jpeg version. What it does do well is show them in detail.
Have you installed Silverlight and looked at how the Deep Zooms work on my site or are you just being theoretical?
That's why I qualified my Silverlight statements with the "exclusive" statement. If you have a backup option which fails elegantly (ie. the site defaults to JPEG automatically if it doesn't detect Silverlight) you should be ok most of the time.
My point is not to lambast Silverlight or Flash, although I'd be glad to do so as there are better, non-proprietary options for 99% of uses those are used, and Silverlight is becoming another widely abused plugin just like Flash. Fortunately Apple and Youtube are killing Flash, and Silverlight is DOA for same reasons.
My point is that if your business relies on web presence to generate sales, it's better ROI to use tech which is widespread and doesn't require installation of new plugins. And if you insist on the bleeding edge, ensure that the customers who aren't on that edge can still get to your content so you can still make the sale. If I was running a photography business and my webmaster came to me saying "here's this nifty plugin which will cut your visitors by 10%" I'd get a new webmaster.
I think I have Silverlight, but I waited for 15+ seconds on your site and nothing happened so I left - the zoom buttons loaded but no image(s). I have 10+ mbps connection.