Got my Revo R2 from HLJ last week (you may have seen the pic I tweeted to JD, Yakface and Jesse James over Twitter), and had a few minutes to fool around with him over the weekend.
I'd probably say it's the worst of the four Revoltech Star Wars figures released so far, mainly due to the limited articulation. You can rotate the head and legs, and the "feet" have Revo style ball joints, but so far I've had a tough time adjusting the joints so you can pose them perfectly (with the other figures you can pull the joints apart to repurpose the ball joints, but not so much with R2). The extra wheeled feet are a cool addition for if you want to have a rolling R2, but you can also pose him in the "rolling" position with the normal feet ala a Hasbro fig.
One feature I LOVE is that you can turn the knob/hologram projector on his face and there's a wheel inside the dome that will cause R2's "mouth" light to change from red to blue.
Unfortunately I don't have the Hasbro Black Series R2 to compare it to, but it would have been cool for Revo R2 to have a few gadgets, or maybe a hologram Leia. That's really my main complaint, it's a fine looking figure, and the paint apps are great, but nothing worth going out of the way to get.
I'd rank the Revo Star Wars figures (what we have so far) as follows:
If anyone wants pics, let me know, I've been super busy as of late but can probably spend an evening snapping some detailed pics if anyone wants them.