I played through the original HW (a rare occasion for me in the last 8 years!) and I found that it was a fantastic game. MP eventually boiled down to masses, although the early game was fairly good rock-paper-scissors. It looks like they've improved MP gameplay with components on cap ships, upgrade choices, and static defenses... unfortunately, due to the wide open nature and scale of the 3D space, I think it is a less interesting prospect than top down RTSs due to lack of chokepoints and interesting terrain.
However, SP game was awesome, beautiful, and compelling. It really was unique (and still is) in the sheer enjoyment of watching a huge battle unfold from a distance in the quiet of space, and the missions were fun and varied. I also think they have some of the coolest space ship designs I've ever seen.
The ships in the demo probably represent a fraction of the full fleet types available, at least if I remember the first one right. If you want to win, the key is (was) Ion Cannons + repair ships, and dock your fighters/corvettes like mad, and build about 7 harvesters + 2 mobile resource stations.
In the first, I would build salvage ships, capture the enemy's equal Ions, then proceed to ownage without fail. I couldn't seem to capture in this demo, but early aggressive Ion Frigates proved fairly effective against the AI. I have to say the AI did a pretty awesome job of attempting to counter my fleet in the demo.
Also, formations in HW1 were *HUGELY* important... you often would completely decimate or vice versa based solely on your formations and positioning heading into a conflict. I couldn't find how to change formations in the demo, but I'll just wait to read the manual
I would rate HW2 as a definite buy, if for nothing else because I think Relic will not fail to disappoint in the single player experience, and it will stand out in your mind as a unique, fun game.