I've had my travertine floor in my master bathroom for 2.5 years and so far I love it with no problems whatsoever. However, my bathroom isn't as heavily trafficked as your bathroom might be.

Porcelain and ceramic would be another option. Cork penny rounds could look great too!

There are several different tile companies that make ceramic tile that looks like travertine--that would likely be a more economical way to go + you don't have to worry about the traffic.

You don't have to worry about traffic on travertine if you seal it. We have travertine in our bathrooms and powder rooms. Even on the main level shower walls. DH sealed (did not enhance) with Miracle 511 Sealer over 6 years ago. It's also in our kitchen, breakfast room, sunroom, pantry, laundry room and the heavy traffic back hallway to the garage.

btw, there are different grades of travertine. Try to buy a line that is not filled to the max. Turn over and look at the bottom. You don't want Swiss Cheese... but don't confuse with normal amount of holes/filler.

Here is a link that might be useful: kitchen link

We have travertine on the floor in two bathrooms, had travertine in the entryway from the garage, and only took that up when we tile the entire downstairs with a different travertine (re-tiled it for continuities sake, not because of wear).

Yes, it can scratch or chip (our entryway tile had some minor scratches, but we've tracked stuff in from the garage, have slid boxes across the floor, had workers coming in and out through the garage while reno'ing various parts of the house, etc.). But, scratches and chips on travertine can often be repaired, whereas ceramic/porcelain tile cannot be. I have buffed out etch marks (using a green scrubby) on the honed travertine in the guest bathroom (former cleaning lady set the bottle of TB cleaner on the floor and it left a nice oval shaped etch right in front of the shower).

I've used a tan/brown permanent marker to "color-in" scratches in our travertine as well (color, wipe off any excess with some paper towel or buff with some fine steel wool), and they disappear.

Like allison0704 said, use a good sealer, and choose a decent quality stone, and you should be fine.