I found the Rebel Story to be fun, but depressingly easy, even on hard mode.
The thing I found is, the Empire can't launch Raid Fleets, so they can't directly attack planets behind your defensive lines. So, I basically made Yavin my main ground unit production base, made Mon Calamari and Kuat my main starship production bases. I built the best Space Stations on every other planet I could, and covered every planet except Yavin and later in the game Geonosis. This maximizes your daily credit production and basically makes you rich as hell haflway through the game. I had 3 massive fleets by games end, consisting of 2-3 Mon Cal Cruisers, 5-6 Assault frigates, 7-8 Missile Cruisers, 10-20 Corvettes and Gunships, 20-30 Bombers and 20-30 Xwings and A-wings to back em all up. The big difference between the Empire and the Alliance in this game is power vs speed. Imps have more powerful weapons to bring to bear, but you can defeat them with well-timed manuevers and focussed attacks.
In addition, I had one large ground force consisting of 12 Artillery Units, 15 T4-B units, 15 t2-b units, 20 squads of infantry, 20 squads of Plex soldiers, 4 field commanders, 10 Speeder Squadrons and 8 Infiltrators. I found the T4-B tanks to be pretty much the most effective unit in the game. I never had to fight a defensive land battle. The Imps usually did'nt even succeed in winning a space battle and forcing my fleet off an occupied world, and the few times they did I was able to counter attack before they could launch an invasion.
We'll see if this strategy works in the conquest modes.