The price to get in is $19, which is a buck more than going up the Space Needle. There are combo passes available that make it slightly cheaper to do both ($33 for both. If you are coming all the way to Seattle and doing the tourist sites, how could you not do the Space Needle?). King County residents get in for the low, low price of $15 per person (and they didn't even check our IDs to confirm it). Once inside, there is about an hour plus of things to see, perhaps a little more if you become absorbed into the artwork.
Being from Seattle, I think that there is a bit of Chihuly burnout. We have had his stuff all over Seattle and the region for years, but for many people this may be their first time seeing it. It IS impressive and many people who visit Seattle visit the museum rate it very highly. In fact, right now this is the number one attraction in Seattle on TripAdvisor.