We basically use the bathroom as a cut through to go upstairs, but it's awkward when we have guests.

I bet!

Let the buyers decide.

I personally think it's kinda gross to have a traffic pattern through a bathroom. I'll bet that more people agree with me than not. I'd close that sucker off in a minute.

I have two doors on my first floor bathroom. One door leads to the foyer/hallway and the other door leads to my office.

I think the two doors are fine.

I don't think it will affect your resale value. These kinds of connected rooms are common in older homes, and unless you've dramatically changed the character of the home it won't be out of place.

I assume there are other options to reach the stairs other than going through the bath? If not, that may be a concern for buyers with more modern sensibilities. Most of us today wouldn't want to *have* to use a bathroom as a hallway.