its HUGE! (the 910xt)

How does it compare to the size of the 310? Looks about the same?
I have small wrists too and my 310 looks like that on mine. No big deal... try it and see! 

(MUCH better than the weird angle of the 305... that thing bruised my wrists sometimes)

http://www.dcrainmaker.com/2011/10/garmin-forerunner-910xt-in-depth-review.html

This will help you with the comparison, as DCRainmaker shows pictures. It looks like the 910 is slightly smaller..there's no "angle" thing like it is on the 305, so. Overall, it looks similar in size. 

If you're used to your 305's size, you'll be fine with the 910.

I agree, on me the 305 looks huge, but after a while it's not too bad, you just get used to it after a while. Women do have to accept manly size. :-)

x2.  I wore my FR60 (with heart rate strap and footpod) for IM Louisville last year.  Since it is a non wetsuit race, I have heart rate data from the time the gun went off until I crossed the finish line.  Also, I have the per mile splits from the run.

If it was giving me the data in order to race properly and train properly, yes.  I have the 310xt now and am getting the 910 tomorrow.  I don't race with it on my wrist.  I just leave it on my bike.  I will probably do the same with 910xt.  As far as training I will train with 910xt in the pool as long as it is accurate.  If not...back to my Timex Ironman watch.  

Yes, it is very big on your wrist. About using it in general, that is your call. Depends on much you really need the data, and what you're going to do with it.

But, about swimming with it, I absolutely recommend that you do not swim with it in a race or in training.

Unless I am working with an elite swimmer, I recommend to my athletes that they don't even swim with a watch. It adds drag, ruins stroke symmetry, and harms feel for the water. And that thing is way bigger than a watch.

Yes, I do. Been doing it for a few years.
And I swim with it, too!  

Really not that big of a deal for me. But only you can decide for you.
  

You're right, it's not a big deal. But I can tell you this, in the water, you are paying for it, as something that big on your arm measurably increases drag. Try some all-out 100s in the pool with it and without it. Do 10 of them and switch the 100s so that every other 100 is with the garmin and then without. You'll see a difference.

If you're already wearing a watch, a Timex Ironman for example, would it really make that much of a difference?

How many seconds are we talking about?

twomarks

Little wrists = big heart,,,or something like that!

I would race with it,,,you will get accustomed to it.