If your love of pinball depends on the stuff that's been standard in pins for 20 years (speech, multiple levels, multiball, DMD graphics, video modes, ANY modes, etc.) then you won't like Flash. But as far as good basic easily understood game rules and kinetic action, it's one of the best! Drop targets! Sweeping shots! There's a reason Steve is known as the Master of Flow.
In addition to the often-flaked backglass, you'll also frequently run into ones with very worn playfields, just because they got so much play. Still worth picking up in that state, just price accordingly. Oh and of course look for leaking batteries like with any Williams game!
Things to make sure are working once you buy it:
-- Flash lamps!!! This was the first pin with flash lamps, and if they don't work, it takes a lot away from the game.
-- Drop targets - the ones in this era were problematic, but can be fixed.
-- Plunger shot - There is an adjustment to make sure the plunger shot properly crosses the playfield and goes into the top lanes, rather than bouncing into the middle of the playfield or rattling around in the upper left part... but nobody ever noticed it or used it. So you'll need to spend some time tweaking that to get it right. Don't forget to check the plunger nylon sleeve. If that's broken and sliding out of the casting, you'll never get the plunger shot to be consistent.
Duncan