In answer to your question.  I have owned both Sega and now Stern machines and honestly can't fault their performance.  Yes they may feel and sound a bit different but as far as reliability goes, as the other guys have mentioned, once they are up to scratch they perform just as well if not better sometimes than other bigger name machines.  I would definitely throw Data East machines into that category as well.

As for dealers, yes there are some, not all, out there that will be happy just to take your money giving you false promises and hopes that your machine has been shopped out and is working 100%.  Don't rush into buying anything from anyone and do your research.  Typically a machine from a collector and/or forum member will get you a machine that at the very least is as described and more than likely will be working 100% and play very nice.  There are plenty of guys up your way that would probably be happy to inspect a machine for you and likewise if you are looking to buy a machine from elsewhere.  No-one likes to see a person new to the hobby get burned.