This is one of the most Epic RTS of all time. The Campaign is excellent (althrough quite repetitive except for some special missions). Oh and also the Cutscenes really really well made. But the difficulty is not so high except for 2 missions in particular : the Harkonnen Civil War playing with Gunseng and, of course the Final Mission.
All 3 Factions are well designed and have their own strengths and weaknesses. The 5 sub-House offers incredibly powerful units which can turn the tide of battle easily.
The gameplay is something kind of "déjà vu" because of its C&C mechanics but I don't mind it.
On the other hand, this game have, in my opinion, one of the best Soundtracks of all time (too bad, we hear them all only in Campaign Mode).