I've been inside the HP lounge at Mission Space many times.
My dad worked for HP, and he won some award the year they opened Mission Space, so they flew him (and a bunch of other people who won + their spouses) to Disney. Then there was a big party after Epcot closed one night and everyone got to ride as many times as they wanted and chill in the lounge.
So the next 2 visits we would head straight to the special little entrance, my dad would give his name, and they'd unlock the door. There was a hostess, comfy chairs, free pop/juice/coffee, a computer with email access, and one of those M:S video postcard kiosks. Most of the times we went in there, it would be just us and maybe 1 other family. My mom would chill in the air conditioning while we were escorted by the hostess to the fastpass lane (where it meets the other lines). From the lounge there's a really dark tinted window that looks down over a part of the line. Very cool.
We always get park hopper passes, so on the way back to our resort from whatever park, we would run over to Epcot, do M:S about 3 times, then head back to the resort. My dad (and his boss, who also won that award that year) quit his job at HP and they started their own business, and my dad says that the lounge is the thing he misses most about working for HP.