For anyone who doesnt know there's some new MGR DLC featuring "Jetstream Sam" who's pretty much the main antagonist throughout Rising. (or at least the most well developed)
It's set before the original game starts and loosely explains Sam's motivations for joining the PMC group "Desperado".
Sam controls completly different from Raiden, he's much slower and more methodical but has the ability to 'quick draw' which unlike Raiden's quick draw can be chained into combos for different effects. He's also a lot more versatile in the air with the ability to double jump and dash. (kind of like Dante)
I enjoyed it, beat it on normal which was surprisingly challenging given that i'd beaten the original game on very hard and managed to get all those secret 'kill x boss without taking damage' achivements. The VR's were a pain (thankfully no stealth) but the interesting thing is they were integrated into the levels themselves and often gave you rewards. (besides BP) As uninventive and drawn out as they were (compared to the DLVR missions) It did provide a break from the somewhat bland enviroments recycled from the main campign.
I wouldnt recommend this for most people (unless you're the type to go after collectibles and achievements) as it's kind of overpriced for what it is. Personally I would have rathered the ability to play as Sam throughout Raiden's campign as it's much better. (sort of the same way I felt about Vergil's Downfall)
If you've already beaten the original game but arent the OCD'ish type I'd recommend just watching the cutscenes on youtube, as they're clearly where most of the resources for this DLC were spent and they're pretty awesome.
If you have any questions let me know. (I havent found all the collectibles, so no help there)
(sorry about the walls of text this was supposed to be a review but apparently this doesnt qualify as proper DLC)