A co-worked does tris and I asked about the little seat on the bike...and she said that you really don't spend much time on the seat. Really?

I thought you spent a lot of time on the seat. Apparently I am not biking correctly!
Is it really important to wear bike shorts/compressions shorts when biking?
Stacie
I would guess what your friend meant is that she doesn't use "much" of the saddle, so it doesn't matter to her that it's so little. I can't imagine that she meant she does most of her riding standing up out of the saddle, unless she is super-human!

If she has a tri (or tt) bike, which basically puts the rider in a more forward position--you know, those bikes with the aerobars that look like the rider is lying forward on the bars--she probably only uses the front inch or two of the seat. The back end of the seat is just for looks.

Seriously, in that position, you are so far forward on the bike that you don't use most of the seat, and you're supposed to rest on your "sit bones," which sounds easier than it is.
If you're looking at a road bike as opposed to the above mentioned tri bike, the saddle will matter a little more since you'll sit further back on it. Most road bikes still have narrow saddles, but after a few weeks of riding, it really will be more comfortable.
As far as shorts, I agree with Liz. The bike shorts are much better for any sort of distance, since they have padding to keep the bum from getting as sore.

They also allow a lot of freedom of movement and less drag than running shorts, so it's a lot easier and more comfortable to spin on the pedals.
Good luck on your choice of bike. As others have said, I'd agree that what type of bike you want depends on what you'll be doing with it. I wouldn't advise dropping a lot on an expensive road bike unless you think you'll be riding quite a bit, and I would REALLY do some research if you plan to buy a tri-specific bike, since those bikes are somewhat limited in "what" they can be used for and they aren't as versatile as a traditional road bike.
Have fun with whatever bike you decide!
Steve