Well, I have not yet upgraded to Entrentchment and I find that there is a reasonable amount of collisions, or "quasi-collisions" as described by LORD_KRELL;
"Have a game going with 4 stars, 8 players and just today after the upgrades, 5 ships I built at a factory, made their usual wide turn out, and ran right into a metal asteroid, slowed, jerked around a bit and finally passed it! Yes it is annoying, and I agree that it slows things down a lot. Fortunatly that particular factory was at a planet with only the asteroids and a Starbase. I can't imagine what would take place if it had been at one of my other planets with 15 or so gun turrets, trade port, starbase and other structures in it's orbital path!!"
It may just be that in light of how almost bug-free the original Sins tended to be, such small details were overlooked.
Although, to be fair, it is VERY annoying when trying to move a large fleet through a cluttered gravity well, or if the "all jump together" setting is on with a large fleet.
A reasonable fix might be to have ships plot out IN ADVANCE their courses, and have fleets plot all courses. This might lead to very excessive memory-dumping, with the whole thing having to be redone any time something unexpected happens, but ships wouldn't be crashing into stuff anymore.
Thoughts?