Yes: Cost of installation.

With a regular deck-mounted faucet, your plumbing rough-in is simple and there's no worry about getting the location exactly right since the supply lines come from the wall to your bathroom sink where the faucets are actually located.

With a wall-mount - the plumber must get the spacing and location exactly right - and if there's a wall stud in the way, then it needs to be relocated so that the faucet and handles can go exactly where you need them.

Very helpful - Better rethink my interest in the wall-mounted faucets. Do like the cleanness though.

After I made the above concern comment .......I hoped someone with EXPERIENCE would reassure me .......that THERE IS A WAY to 'get-er-done'. I'm going to print out these comments and go over it with our builder (and maybe ask the architect as well).
Thanks so much for your interest and quick follow up. I appreciate it.

It's important to consider the angular projection of the water as well as the concavity of the bowl when determining the height of the valve installation. You need to take into account the finished height of the bowl, the drop of the spout, the countertop and the cabinet. Ideally you would hook up the faucet to a hose outside to see how the water flows out of it if there's angular projection involved. in my opinion, splash is maximized when the water hits the drain. Therefore the water should hit outside of the drain. This is where it pays to have a professional with plumbing fixture experience with your particular faucet. This is the kind of service you get from a plumbing fixture showroom.

I know you are right. I live in Bloomington, IN and the showrooms are limited although the existing businesses are well known and respected....just a limit on what you can see in the showroom. This is why houzz.com or going to Indianapolis are helpful. I appreciate all your comments. You are in CA....correct?

Yes. We're in Santa Cruz, CA. Been here for 25 years! I wish there was more of me to go around!

Ditto. Thank you very much!

The wall mounted faucet is a simple and elegant look. if your contractor can get it right and you have a good plumber, you should be able to enjoy it for years.

Thank you also for your re-affirmation that I CAN do it - with the right plumber. I have confidence in my builder too.

One more thing: brand is REALLY important when putting ANY fixture in the wall. Brands go in and out of business. If you're committing to it in your wall, it needs to be a major brand which should increase your chances of getting parts.

By the way, the same rules hold for shower valves. Major brands purchased from a trusted retailer.