How often do USB to PS/2 adapters work?

[Jt00]

I've been looking into getting a mechanical keyboard and have read about n-key rollover using a PS/2 connector. However, the only full-size mechanical keyboard I can find that uses a PS/2 connector is one made by Rosewill. I've been wondering why people don't just buy a regular USB keyboard and get a $2 USB female to PS/2 male adapter. After some research, I found that a problem some people have with this adapter is that their keyboard doesn't have the option to go into "PS/2 mode" when plugged into the motherboard's PS/2 port.
Does anyone know how common this problem is, or how widespread the support is among USB keyboards to be able to switch to PS/2 mode?

 

[Phillip Corcoran]

The USB-to-PS/2 adapter problem is very common.

You can find a few more native PS/2 keyboards on Amazon website, I got a couple of "Genius" brand (one for a spare) last year.

 

[VincentP]

There are plenty of USB keyboards with N-key rollover. PS/2 is a thing of the past.
Even 6 key rollover would be fine.
Here is the keyboard I use, which is just one example:
http://www.corsair.com/en-au/vengeance-k60-performance-fps-mechanical-gaming-keyboard