Random impressions from a big time DMC fan that has more or less been ignoring DmC up until this point.
Sons of Sparda mode is pretty challenging. Not hard, but it's a challenge. Enemies seem to ignore attacks more, and will sometimes attack out of grounded hitstun forcing you to play very defensivly. When there are multiple enemies on screen, you spend a lot of time moving around with hit and run tactics. Very movement based. The basic fodder enemies also block a lot more, which is par for the course on harder difficulties in DMC games. The new shield guys that are only vulnerable to one weapon also makes things a bit interesting. Gotta be careful not to accidentally hit them with the wrong weapons when there are multiple enemies on screen or you're pretty much guaranteed to get hit. It gets tougher when both types are on screen at the same time. Lots of dodging involved. Also has a new flying type enemy and they seem to shrug off all attacks besides Helm Breaker and will attack you mid-combo. After I got used to combos and dodging, they were pretty much the only ones hitting me.
The boss on Sons of Sparda mode is tough, and it feels similar to the usual DMC fair of figuring out the attack cues, dodging/avoiding the attacks, then going in for a few hits and repeating. I think it might have new attacks in SoS mode, but I don't really know for sure. I killed it pretty fast on normal, so I might just not have had the chance to see them.
All in all, I think the game is pretty fun when you get the hang of it, and this is coming from a guy who played like 800 hours of DMC3 and DMC4 combined. I wouldn't put it on par with them from what I've played, but it's a solid action game and has quite a bit of depth. The framerate is disappointing, but it doesn't seem to affect the ability to combo/dodge any so at least there's that. I'll still probably wait for the PC version, though.