There are several ways in which Vegas makes me think of sponge.
1. It is the most dehydrating place I have ever visited. After a 10 hour flight, you arrive shrivelled to your air conditioned yet smoky hotel. Whence you depart only for short walks in the desert air or in air conditioned buses. It sucks all the moisture from you. The lovely lovely waitress at the Stratosphere tower said as much, noting that we English would soon need to return to our humid environments. This makes San Francisco, home of London-esque greenery and freezing fog, the ideal place to move on to for comprehensive rehydration.
2. On holiday, I am generally in 'sponge' mode - absorbing all the new sights, sounds and so on. Even for a Londoner, though, Vegas is over-stimulating. The lights! The beeping of the slots! The salespeople! The multiplicity of alarming statistics that prove how Vegas defies nature! The flicking of the callgirl cards in the street! The number of shops! The size of the food!
3. Jet lag makes my brain spongy. Vegas doesn't help with that. It is full of things that make you go 'aaaaargh' and clutch your skull in sheer bafflement.
All of that said, I am delighted to have seen it once. Our friends' wedding was lovely - Vegas appropriate but not tacky. We saw two incredible Cirque du Soleil shows and a great gig by Franz Ferdinand (the less said about Bloc Party who were actually heading the bill the better - we left). We enjoyed siberian nachos at Red Square for my birthday. We gawped at the hoover dam and squeaked in adoration at the antelope ground squirrels who ate from our hands nearby. We shopped, we took endless pictures to prove how mad it all is, I developed a mild devotion to Wallgreen's pharmacy for their range of lotions and potions, and we spent some time trying to calculate how rich we would have to be to stay at the Bellagio and watch their exquisite fountains all evening.
So I had a great time in Vegas, but it's all just so very very wrong. As typified by the timeshare salesman who pointed out that the next big project is a water park and ski slope. In the desert! Right before he drew our attention to the singing rocks on the communal patio...