Soulstorm is an "expandalone" in the splendidly bloody science-fiction strategy series, Dawn of War. That basically means that Dawn of War is getting a little pricey if you want to keep playing the same game, but with the extra races. They're not a bad idea if you fancy a dabble: there's no need to have the original game, and there's some new stuff bolted into a proven and familiar game. Nevertheless there's a sense of vacuity. Nothing much is being achieved by this game, and there's really nothing new to focus your attention on.
Still, someone must be making a few quid out of these expansions, since they can't be all that expensive to develop - the tech has been around for four years, and the previous races are bundled each time, with the same skirmish maps, the same art assets, the same (if slightly tweaked) army builder, and so on. It's a pity the people who actually made this game - Iron Lore, who went bust last month - won't see a penny of it. Jumping into the mire of the Games Workshop universe didn't do them any good at all.
But it's not something we need care about, because I'm sure you'll be able to pick this up for next to nothing in a couple of months. And that's what I'd recommend you do. Right now it's difficult to recommend adding this to a Dawn of War collection if it already includes everything up to Dark Crusade. This latest iteration adds two armies, Dark Eldar and Sisters of Battle, and delivers another non-linear campaign mode, but none of it's entirely vital. And of course it's only partially standalone, since it requires the original Dawn of War if you want to be able to play with Orks and Space Marines. And if skirmish or multiplayer are your thing, you're probably going to want them too.
Anyway, we're now up to nine factions in the Dawn of War universe (bio-swarming Tyranids notable by their continued absence) and the two new races are of mixed appeal.
The weakest of the new duo are the Dark Eldar. They have a squeaky-voiced piercings-and-slavery thing going on. They have some spectacular flying-boat type units and some black-and-purple-energies. It all feels somewhat contrived, and in the steroids-and-cybernetics overwrought universe of universe they're very much the leftover race. The normal Eldar might be a bit emo, but they've got some class. The Deldar are awkward pubescent posers, like they did Chaos but didn't inhale.
The Sisters of Battle on the other hand are much more entertaining. They're the ultimate religious zealots of their 40k universe, seeking out and incinerating heretics when and wherever they find them. Their high-end units have a suitable madness to them - a penitent tied to a crucifix-robot, a church pipe organ-tank that acts as a rocket-bombard, and a giant angel raised from the dead by the psychic ghost of the Emperor of all humanity. Yeah, that's the good stuff.