"Rudimentary, Elementary Design: Pain In The Arse? Yes, Always."

That may indeed sum it up.
I'd have to see it for myself , but my initial worries (may be wrong). Is screen refresh and the fact you need another piece of hardware to visualize.
Imagine a scope where, if you hold the probe to a signal you het an update every few seconds.
Of course it is open source and all , but that incurs another question. Of the people buying it , how many will be really proficient enough at linix and xilinx , vhdl to actually make meaninfull additions to it ? Just because a million people have the source that doesn't mean anything ...
Look one million people have a ferrari in parts... If they just knew how to put it together (a few may be able to do that) and have a drivers licence ... But first i'll need to get a job to get money for fuel ... And in the country i live, roads havent been invented yet ... You know, along those lines...
Of course i applaud the effort. As for practicality and usability... Dunno. Maybe with some more spit and polish.
There was another comment. Why on earth sma. My thoughts also. Sma is a comnector designed to be mated once in its life (using a torque wrench) and be left alone. If they had put on 3.5 mm connectors... ( no they are not the same ! 3.5 is designed for frequent mating. ) and, at the frequencies they are mucking with, BNC would have been perfectly fine.
Also, the strange angles of the comnectors will make a housing for this thing a pain... If im going to use this a stest equipment i dont want to have a bare board on my bench. The bench is full of pieces of solder ,spent solderwick, snipped off component pins, stubs of wire. Box please ! Any test equipment has a case. Sure it looks 'cool' , but test equipment needs to be robust .