This United Club location was the nicest one I've been to. It has a great view (including of the Strip and surrounding mountains) and plenty of comfortable seating. The snacks were great (freshly-baked cookies, cheese and crackers, snack mixes, and fresh apples and bananas), as was the open bar (premium liquors and certain beers and wines cost extra).
TIP: I get passes to the Club through my credit card, but found out recently that you can also buy passes on eBay pretty cheap... totally worth it for the comfy seating, open bar, and good snacks. I would definitely suggest doing that any time you think you might have a long delay or layover at an airport that has a United Club Lounge.