To clarify things a little, this has nothing to do with "snifters," which are glasses with large round bottoms that people usually drink brandy from. This is about the very small and narrow whiskey glasses, usually saved for fine single malt scotch whiskies. Specifically it is about the Glencairn design, popularized in Scotland:
I think Mark's issue with it has to do with esthetics, but I'm not sure. At any rate, I'm usually willing to try anything once, so I put one of my glasses (an empty Riedel whiskey glass) under the portafilter. But I had to tilt it so far over to get it under the spout, it would never work. Maybe I'll try a bottomless.
This does open the issue of aroma in espresso. I think aroma is the most important feature of drip coffee, which is why I use Offero mugs. I've always assumed that crema blocks the aromas in espresso (besides which, I drink them quickly). But, maybe I'm wrong.