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An attraction at the Las Vegas Hilton. Located in a space-themed portion of the casino (featuring such things as slot machines with no handles -- you put your hand through an electric eye to start the reels. Ooh.) The "Experience" area features a couple of merchandise shops (with some pretty cool and reasonably priced stuff, surprisingly) and a small restaurant called "Quark's Bar".
Quark's Bar itself is worth a visit. It's like a small version of the bar from Deep Space Nine, only without the Dabo tables. You will be served by either a Ferengi bartender or attractive random alien waitress. Prosthetics, etc., are disarmingly convincing; about the same quality as the television shows. Entertainingly-named and fairly reasonably priced drinks are served in comical glasses. Fairly standard and tasty bar food (onion rings, hamburgers, etc.) are given Space Names and served up. Bartender will chide you about not ordering enough, remind you to leave a big tip, etc., while the waitress will beat him down verbally in return. All extremely in character and very entertaining.
The "Experience" itself costs $12. You are given a time to show up at the entrance. Between the turnstiles and the attraction entrance proper is a very large "Star Trek Timeline", showing the timeline of the various Trek shows along with some props, and then a "Trek Museum", also filled with props. In these areas, you may be accosted by other costumed "cast members", like the buxom Klingon who took a fancy to my brother ("So... tall and strong... growl").
Spoiler section. Now on to the attraction itself. Some may call it a "ride", but the "ride" is really only one component of the "Experience". You are put into a loading area, as if you were about to board one of those virtual reality rides on hydraulics that you see in malls (or like "Star Tours" at the Disney parks). The lights suddenly go out, a swoosh of wind, and you and your companions are standing on a transporter pad with a very confused Federation transporter guy staring at you. He speaks to Riker over his comm badge and leads you down the halls of his starship (which are quite convincing except for the "EXIT" signs obviously required by law =). You get to the bridge and Riker speaks to you and the rest of the crew. "Attacked by Romulans... great danger... bizarre time warp phenomena... must escape in shuttlecraft... etc. etc."
Suddenly, Romulans attack! The bridge crew does the Star Trek "lurch to the side when the ship is hit by phasers" thing. They then quickly lead you to another loading area and this time you actually do get into a shuttlecraft. You "fly" off the ship, Do The Time Warp Again, soar over the Las Vegas skyline, and finally crash into the Las Vegas Hilton. "You will be debriefed, speak of this to no-one, etc."
Big fun and well worth the $12. The ride isn't that great, but the entire experience is piles of fun.