Overall, I liked it. I got it when it first came out, but only recently completed it. I am not an online strategy multiplayer, definitely preferring single player options, so I can see that to maximise the value for $$ you probably need to be willing to play online.
I liked it as it quick paced - some missions only taking 8-10 min. There was an RPG element in that you skill up your squaddies and get some loot (random I think) from various kills.
I did find the overall campaign a bit easy, although I played it only on the medium level difficulty.
I liked the tactical aspect of combat, but sometimes with some bigger battles, particularly against tyrannid swarms, I had no clue what was happening other than my marines were carving through them and I just had to press buttons to heal up, or throw a grenade everynow and then.
There is some (arbitrary) rewards for different play styles. I preferred to clear whole maps, which at times would take 25 min or so rather than the quick style of going straight for the main boss. I figured I would get more loot optons by clearing the map. You score different points depending on % enemies killed, time taken and own team losses.
Overall, I put the game in a 'good category' without being brilliant. I love the 40k universe and story, so that may bias my positive perspective somewhat too.