touring in Europe (tour operators)

I'm planning a bike tour in Europe (most likely France or Italy) next year,
and I wanted to get some feedback on various tour companies. I'm looking
for a tour with a group of fairly serious riders, with some challenging
terrain (Alps, Dolomites, etc.). Tying in with a big race like the Giro
or Tour is an option for me, but not strictly necessary. Luxurious
accommodations (e.g., four-star hotels) aren't a priority -- I'd
rather save some money by going with something a little less fancy, if
that's an option.

Anyhow, I've done a bunch of investigating on the web, and the following
companies seem the most likely from what I've seen:
- Erickson Cycle Tours
- La Corsa Tours
- La Cima Tours
- The Bicycle Outfitter

If anyone has any experience with these companies, I'd be very glad to
hear about it.

Also, if there are some companies not on the list that people have had
good experiences with, I'm open to suggestions!

Kent Wenger