I recently asked almost the same question on another board, when I realized that my not-yet-3 year old is almost 38 inches AND found out about the height requirement on the ride.

Some said yes, some said no (seemed to match up if their kiddo liked it or not), most said "depends on the child". I'd add, it depends on the kid's mood at that minute, which I've figured out over months of figuring out why my brave boy started falling apart in line at the Halloween-theme Haunted Mansion (tired, tired, people screaming at the top of their lungs in the stretching room, and more of being tired).
Since the height is only 35 inches, that does indicate they are cool with a younger kid. I was told elsewhere that the original limit on the ride was 3 years, but there were parents lying about much obviously younger children, so they put in the height restriction instead. That's what I was told, at least.
I have NO idea if this will be useful, but I noticed that the attraction page for the Matterhorn on disneyland.com has a little quicktime movie of the ride. Maybe 5 seconds, but it shows the jittery ride, shows a little bit of what the speed is, and it shows "Harold" (what I've been told his name is!) the yeti/abominable snowman. I've been showing it to DS every so often, to sort of familiarize him with it, while explaining that it's MUCH bigger than that. Again, I don't know if it will help with us, or with anyone else, but it's something I'm using to sort of familiarize him with it, just in case he seems in a brave mood when we're near the ride.