Umm.. I think we are talking two different things here.
A "subway map" is a flat map that shows where, given a system that your ship is in, which systems you can jump to, and which you cannot, without going through other systems.
Its not a real subway, its just a way of creating a map.
Besides which, Sirius is a dump.
As for "worth buying" ymmv. I liked it enough and recognize that this is still version 1.0. And that further developement is dependent on whether there is a market for the product now. If it does not sell now, then the programmers may just give up and work on something else.
I would like to see a host of changes, including the one you talked about. (Slide camera instead of only pivot around a single star) I would like to see more work on the system views to take into account things like eccentricity of orbits. And fill commands for rings and asteroid structures. (As it stands now, rings and asteroid belts are pretty hard to distinguish from planetary orbits. A single line, when a ring structure can be thousands of kilometers wide.)
Also, when looking from on top of the star systems, I have crashed the display a couple times. Not sure what I did wrong, but I think they are getting into a coordinate singularity at the poles.
But considering it cost me only 32 bucks for the thing, that I had it up and running in no time flat, and I have been waiting for some 25 years for exactly this kind of software, I have bought it and look forward to the updates.