Plus-x is my fetish film simply because I started with it, 20 years ago. Plus-x, APX100, HP5 and TMax3200 are my absolute favorites.
I'm so glad to have shot my latest Cuba series on Plus-X. Couldn't imagine using a different film.
As for a substitute? I'd lean more towards Fomapan100 for the look. FP4 would be very easy to get accustomed to but the look is not the same.