Besides the amazingly inexpensive price of these displays, there is also another reason that the Yamakasi Catleap in particular has become so popular with enthusiasts.
Early consumers who received the "2B" revision of the Catleap PCB noticed that it could be driven at refresh rates up to 120Hz. This makes the Catleap an incredible product, because currently, it isn't a matter of money, there are NO other 1440p panels capable of over 60Hz on the market.
A higher refresh rate becomes extremely important when you are talking about gaming with V-Sync enabled. In order to avoid "screen tearing", some gamers enable V-Sync to lock their frame rate to the refresh rate of their monitor. For 99% of the displays on the market, that means your frame rate will never go above 60 FPS. While this is an acceptable frame rate for playing games, a lot of gamers crave more. By driving your monitor at a refresh rate like 120Hz, it should mean that games can run at twice the frame rate without any tearing.
Although these displays may be capable of running at higher refresh rates, it isn't as easy as just changing a setting in Windows to enable a faster refresh. One thing that you have to take into account is whether or not your GPU can actually drive that many pixels at a higher than standard refresh rate.
Pixel clock, or the frequency which determines how much bandwidth a card has available for displaying an image, is a major concern for overclocking these displays. In a simple version for all that we are concerned with here, your needed pixel clock can be thought of as resolution multiplied by the desired refresh rate. This would mean for example, that driving a 1080p display at 120hz would require the same pixel rate as a 2k display at 60Hz.
The issue that many people ran into was that most graphics cards aren't capable of handling this type of bandwidth, due in part to 120Hz, 1440p displays not really being on the market. Beyond having a capable card, drivers need to be hacked to unlock these higher refresh rates in a lot of cases.
The good news is that most of this work has already been done for you. The excellent "Yamakasi Catleap Owner's" forum and overclocking subforum on 120hz.net are dedicated to these displays, and running them at the highest possible refresh rates.
However, the bad news is that it seems these displays aren't really being produced or sold in mass quantity anymore. There are a few sellers on eBay marking what they claim to be overclockable monitors upwards of $500, but there is even more risk when buying from a seller like that. Once again I will point towards 120hz.net, who has been organizing group buys of these overclockable monitors, currently at $555. This seems like it may be a more reasonable solution than eBay, but you really have to know that you want one of these displays to fork over the extra money.
Also be advised that your mileage may very even if you get a "2B" SKU. Things such as different GPU driver releases, and various anomalies with the displays themselves mean that you don't exactly know what refresh rate you will be capable of, but it seems to be a pretty safe bet that you will at least get around 95Hz.