Well, I do mind ship combat because I have Sea Law, which has all the rules and crit tables for it, AND I have stripped it down and made it even faster and easier (I have other games I play when I want a good tactical simulation, not rpg's).
The SM rules are also fast and simple (one attack table, various types of malfunctions/damage). The SM table is designed to equal 1 hit/ton (so a 30 ton craft has 30 hits and is obliterated if it takes 30+ hits), but it aint hard to mod the hit/weight ratio down for cars and the like.
We...well, not me, but OTHER GM's have mixed games systems with SM, the most memorable being Battle Tech, which has a simple hit point system but is well fleshed out. I tried to marry HERO vehicle rules to my RM/SM games, but I did not fully enjoy the results and have not tried again.
Still, as a GM, I basically wing vehicle combat...or avoid it
lynn