Posted 23 March 2007 - 05:13 AM
I have read somewhere or other, that a 50mm lens doesn't compress perspective enough, and therefore some people don't like how big their noses look if used in a portrait. I've heard that around 80 to 85 mm is perfect for a portrait, for the same reasons.
The reason I got the lens with the IS is that I have developed a very slight shake in recent years, and I needed the added stabilization when not using a tripod. If you shoot in a studio setting with your camera on a tripod, you won't need the IS. I'd say investigate third party lenses. Tamron is supposed to make a lens (forget the spread, but it's similar to the 28-135) that's highly praised by its user, but is actually cheaper than the Canon.
As with cameras, lenses come in so many varieties, you really do have to specialize it for your needs, and ignore others' needs. Myself, I haven't been sorry about getting my 28-135, but I have noticed myself over-trusting the IS sometimes, and not taking my time, thereby getting unnecessary shake.
Best of luck with the search.
--Chris