The Ironclaw is equipped with a PMW3391 optical sensor, which seems to be a Corsair-specific variant of Pixart's PW3360 that goes all the way up to 18,000 CPI. Every version of the PMW3360 I've tested has shown itself to be a top notch sensor, and the PMW3391 is no different. The sensor served me well in high-intensity matches of Unreal Tournament 2004 and Ironsight. My shots connected just as expected, and nothing felt off. I was unable to get the sensor to spin out or lose tracking, even when slamming the mouse down onto the mouse pad at odd angles.
The sensor passed my mouse acceleration test without a hitch. The test consists of moving the mouse back and forth between two books and checking to ensure that the crosshair returns to the same spot whenever nestled against one of the books. I perform the procedure in CS:GO with raw input enabled and mouse acceleration disabled. The crosshair moved smoothly between the two points without any noticeable built-in mouse acceleration. One-to-one tracking is needed for building accurate muscle memory, so it's important to use a mouse without any mouse acceleration for gaming.
The PMW3391 produced fairly smooth curves in MouseTester, which is a good thing. There are a few more irregularities in the curves than those produced by some other PMW3360 variants I've tested, but such small imperfections at the millisecond level shouldn't be problematic during use. I certainly didn't notice any issues while gaming or editing photos.
The sensor's max polling rate is listed as 1000Hz, and MouseTester confirms that number. The update period is about once every millisecond.
My attempts to draw smooth lines in MS Paint show that the sensor doesn't have any native angle-snapping. Angle-snapping is another inhibitor of one-to-one tracking, so its absence is greatly appreciated.
I took a look at Corsair's iCue software recently in my review of the K70 MK.2 Low Profile Rapidfire gaming keyboard. I had some issues with the software that are only heightened when it comes to mouse settings. iCUE tries hard to look slick, and it does look better than previous iterations, but unfortunately the usability is not ideal. The interface is more cluttered than it needs to be, and settings are divided up into superfluous tabs. The functionality is there, but it can sometimes be confusing or somewhat of a chore to accomplish what you're trying to do.
Corsair's new Ironclaw RGB gaming mouse is solid all around, but I have a few nitpicks. The scroll wheel feels a little cheap, and the thumb grip is somewhat short. iCUE can also be a bit of a pain in the neck, but once you fine-tune the mouse to your liking, you can ignore the software. Otherwise, the Ironclaw is fantastic. It's large and sturdy, with a shape that has broad appeal, and Corsair kept the weight down to 105 grams. The buttons are satisfyingly clicky and well placed, the braided cable is malleable, and the sensor is reliable and devoid of built-in features that hinder tracking. If you like bigger mice good for a palm grip, the Ironclaw RGB is a great choice for $60.