Sorry I haven't used your unicode operator add-on yet. As I explained,
right now I am doing all open source development, so I currently need to
write source everyone can use. I do think this would be a good language
integrated feature. I am thinking of your examples of math-oriented
analysts like actuaries, etc. able to integrate the math and logic
symbols they use right into the language. (So that is feature #1.)

Feature #2a. I have been busy adding Functional Data Structures to
FSharpx.Core.Datastructures. There are now many (and more to come)
structures that implement "cons", "head", and "tail". It would be very
good if the List cons operator :: and cons pattern discriminator ::
could be reused by other data structures that implement cons, head, and
tail. Perhaps this could be done through an interface, call it ICons or
IHeadTail, or something like that. (Reference IRandomAccessList, IDeque,
and IHeap in FSharpx.Core.Datastructures.)

Feature #2b. Several FSharpx.Core.Datastructures structures (more to
come) implement snoc (the inverse of cons). A reusable snoc operator and
pattern discriminator would be good (I propose ;;). Once again maybe an
interface could enable this. (Reference IDeque and DList [conj in DList,
which could be implemented with a proper name of "snoc"] in
FSharpx.Core.Datastructures.)

Feature #2c. Easy reuse of some other operators. I haven't experimented
much with others, so I might be giving you a wrong example, but I think
there are issues with re-using + (plus), for example.

Feature #3. Not really a language feature. I have never used
Mathematica, but I have a vague understanding of Mathematica Notebooks.
An integrated scripts / type provider explorer / graphics environment
with intellisense and integrated help like this would be great.

Thanks for your interest in my opinion and your great work on F#.