I think the fact that VFF exist together with Christopher Mcdougall's book Born to Run are the best thing to happen to running in recent years.
1. For years if running hurt, the canned advise you'd get is either your body isn't built for you to be a runner or it was time to go back to the running store and spend $100 or more on the next pair of even more technologically advanced running shoes. No mention that your running form might just be at fault.
2. For years the type of running shoes were sold based mostly on arch height, ie if you had flat feet you were told to buy motion control shoes. Very little look at the mechanics of how you ran.
Vibrams have been the conduit for both of these to be questioned and introduced many people to ideas such as the prose method of running.
I'm not a full convert of vibrams (still put in most my miles in 'normal' running shoes), but I think vibrams, true barefoot or some other minimalist shoes are a great thing, at least as a training tool. After starting running in vibrams, I've adjusted how I run to shorter, quicker strides with a more mid-foot strike (vs heal strike). While with scientific community hasn't come up with proof that barefoot running can help with all the things many people claim they can, since I've started I'm faster, can run further, and haven't had a running related injury, so I give it two thumbs up.
I haven't seen any Vibrams in a tri yet but I saw a lot of them at the P.F. Chang's Rock 'n' Roll Marathon here in Phoenix at the beginning of the year. I'm not sure how cumbersome they would be getting on in transition during a tri but who knows. I'm all about minimalist running though. I had to work on my efficiency and foot strike so as not to injure myself and transitioned gradually from "standard" running shoes to racing flats. And I'll never go back
"If you set a goal for yourself and are able to achieve it, you have won your race." Dave Scott
I run fairly often in my vibrams. Here's my take:
To start with, my running style has me striking the ground with the balls of my feet. Therefore, I did not need to change my stride a whole lot when I began. I can imagine if you are a heel striker, it can and will be painful until you adjust (think gazelle). My usual workout in them consist of an hour long run on pretty variable terrain, 2-3 times per week. Like any new workout though, an hour took a few months to get used to. The first thing I noticed when I started running is that my whole lower kinetic chain felt much stronger( butt, thighs, calves especially, and even the muscles in my feet). My feet even started to get wider. Though I would note that I have very flat feet, so any added strength in my feet helped tremendously. When I would run in my normal running skeakers on weekends (hashing= a 45min to 2hr trailrunning race), it would feel about 50-100% easier. The added support (especially in the heel) of the sneaker literally made it easier to run after training in Vibrams. I would definitely recommend them for TRAINING a few times per week, NOT PERFORMANCE. Slowly work into a training regiment with them, both in speed/distance and time. Otherwise you'll end up out of commission if you push too hard, too soon. One time I only skipped 1 week and I couldn't believe how sore my legs were. I was down for another 3 days before I could even run.
Ultimately, they are a great training tool for cardiovascular exercise. People will think you're wierd, but then if you've already bought them you may be heading down that road anyway (pun intended). I also suggest road, grassy (felt the best), or sandy surfaces. Rocky surfaces (i.e. service roads) are a big no-no.