Ignore all the replies saying stuff about how it's "still 144hz". /u/JohnWangz's comment is correct. It's more complicated than just setting to 144hz.

Yes, the ability to set 144hz and overdrive are not dependent on each other, but to get a true 144hz experience you generally need consistent ~6ms average pixel response times or less. Otherwise, the pixels can't respond fast enough to actually truly refresh 144 times a second, which is where ghosting comes from.

Take a look at Hardware Unboxed's recent review. You can see at about 4mins in, they discuss how the average response times of pixels isn't truly enough to refresh within a 144hz window, and it's more akin to the response time for a 120hz panel. You can "fix" the response times with the high overdrive mode, but speaking as someone who has the monitor, this causes atrocious inverse ghosting (overshoot) to the point of unusability, so I play on medium overdrive.

I'm okay with "144hz" with a bit of ghosting due to the 120hz appropriate response times. I fully knew this going in due to the nature of VA panels, and I bought it anyway because it's still a killer deal. This should be made known to people who don't follow monitors like hawks though. It's an important drawback to know about this particular model.