I say get it. Definitely a good deal for this.
The board itself would normally run you $300+ (depending on which version it is), and to find it in the coveted big blue cabinet, BONUS!
If you go check it out, take note of the version of the board when it boots up. The Asian version is worth more than the USA version. I'm not sure of all the differences, but I remember reading somewhere that the AI in the Asian boards is smarter and lot less cheap than the USA versions.
Also, ask the seller about the suicide battery, when it was last replaced. CPS3 boards have carts with a suicide battery installed, that kills the game dead when that battery runs out. I'm not sure whether it was a anti-piracy measure, or a ploy to having ops continuously require servicing from Capcom...either way, it's annoying to have to deal with it (one of the downsides of owning CPS2/3 hardware).
This page explains a bit about them:
http://www.arcadecollecting.com/dead/dead.htmlGood luck!