i have an x-arcade 2 player unit that i used for my control panel. I had used it just like it came for about 2 years before i decided to build a cabinet. when i did, i figured i'd just gut the x-arcade and build my own panel, thats where the fun began. the wiring is way too short, i had to extend the wires on about half of the controls, which was very time consuming. (i made little extensions with crimp on connectors, so i could put the x-arcade back together someday if i wanted.)
it works well, now that it is done, but unless you are making a very narrow control panel, wiring could be a mess. i dont know if the wiring in the build your own arcade kit is any better or not. as for the buttons and sticks, they seem fine. i dont have any first hand experience with any other brand of sticks, so i cant really compare them. they all make a fair amout of clicking noises, but that doesnt bother me. you can buy the two sticks and 20 buttons for $30, which is a good price. lots of people say they dont like the sticks...but i dont have a problem with them. ( i plan on replacing one with a magstik plus here soon to solve my 4way issues)
the best part of x-arcade is the console support, as far as i know, it is the only system compatible with xbox, Playstation/playstation 2, dreamcast, and gamecube. (looks like a 360 adaptor is still a while off, due to microsoft restrictions on peripherals).
i have a dreamcast in my cabinet, as well as a pc, switching controls between the two is just a matter of flipping a switch. works great. also with teh x-arcade on the PC, you can have 4 different button configurations, so if you have some games/emulators that just wont let you customize the controls like you would like, you can do it with the x-arcade. (i use two, one set up specifically for playing DOOM, and one for everythign else)
i am happy with my x-arcade, although looking back, i probably would have went with an ipac or similar encoder...
as for tekken and soul calibur, i dont know about the rest of you, but they dont run to well on MAME for me anyway. unless thats where the consoles come in to play.
a dreamcast is great for fighting games, and with the x-arcade and the dc vga adaptor, it is very simple to integrate into your cabinet