It is a pretty standard 4X tech tree where you just get a boost to the same stat over three/four upgrades. I'd really like to break that formula though and throw techs in there that aren't quite so linear, such as Tech A increasing range and rate of fire for a certain weapon but Tech B reduces a bit of your fire rate for boosted damage (you'll still come out ahead in terms of DPS though).
Weapons are percentage-based and have four main stats: range, damage, rate of fire, and shield negation (this last one can be safely ignored since the only thing that could use shields is the Custos-X). No accuracy boosts since weapons are 100% accurate in Sins.
Hull, shields, and antimatter (mana) all get percentage boosts to maximum values and passive regeneration, and shields can get their passive damage mitigation boosted as a flat value.
Armor gets flat boosts to armor points.
There's also the odd-man-out of mass reduction which gives you faster ships.
Of course we have the usual 4X economy boosts such as increased income, faster build speed, reduced costs for things, etc., so if you think there's any good economy techs that could be put in a military tree, go ahead and post them as well.