The Venetian's Guggenheims are actually two separate exhibits with two separate entry fees.
The Guggenheim-LV installation through June 2002 is The Art of the Motorcycle. This exhibit originally opened in New York in 1998; my brother, a motorcyclist, was so thoroughly blown away by it that I knew I needed to see it eventually. My parents, husband and I started with the Motorcycle exhibit. This is a LARGE exhibit, fascinating in varying degrees for different members of our party. My mother lost interest first; her interest in history was tickled by the very old bikes from the late 19th century and she was intrigued by the advances in paint and aerodynamics, but ultimately, she was not interested in scrutinizing each model. She went to relax by the computer stations on one side of the upper floor of the exhibit. My husband and I had equal interest in the technological developments. I found out that I really favor Indian bikes and my husband now wants a Harley. We felt ourselves fizzling by about 1986, agreeing that we didn't know enough about motorcycles to appreciate contemporary adjustments and subtle changes to styles. My father, being the most mechanically savvy of us all, went through the exhibit at a much more leisurely, contemplative pace. We did not feel strained waiting for him, however. We had each other, ample seating and a cool DVD system to putter around on until he caught up with us. If you are a true connoisseur of the motorcycle you might take well over two hours there. Maybe all day!
The Guggenheim Masterpieces and Master Collections is a laudable collection of Impressionistic through Early Modernist works. Currently, the rotating installation features the "Guggenheim Hermitage" a joint exhibit with works on loan from the Hermitage. We saw all 45 paintings in an hour or so. As we are used to the Met, and I have been to the actual Hermitage, it felt like an enjoyable mini-blip of a museum. This should not discourage frequent museum-goers; there were Chagall and Picasso there we had never before seen (and may never see again, truly.)
Unless you are going on a Monday or Tuesday during a non-convention week, I heartily recommend buying tickets in advance. You may buy online by navigating www.venetian.com, but I was unable to get the site to give me the $5.00 discount for buying tickets to both exhibits so I called: 866-GUGG-TIX. Each exhibit is $17.75 for adults without discount. The service charge for each reserved ticket is $2.75, basically, you almost break even and are assured of being able to enter the museum at your preferred time. Ultimately, we paid $152.50 for four double admissions, picking up our tickets at Will Call, bypassing the line. We reserved 2 pm entry for Motorcycle and 4 pm for Hermitage; that works out just right with a bite in between. With no snack, I'd put 90 minutes between entry times, if doing Motorcycle (casually) first.