Repetitive. If you've played the demo, you've played the game.
Wet really tries to hit it's tone and attitude down pretty hard. It does a good job of that, with both the voicework, gritty film layer, outrageous actions sequences and a fitting soundtrack. It's enjoyable for a short while, with some of the acrobatic moves being a genuine thrill to pull off... but the novelty of them run out far too quickly.
I found myself doing the same moves over and over to dispatch most of the enemies. Either jumping and shooting, or sliding and shooting, nothing more. Rubi can gain extra weapons throughout the game, but they don't seem much different than the two standard unlimited ammo guns she carries from the start. The only one that seems mildly different is the crossbow, but even so, it comes so late in the game you'll barely have a chance to use it... and never against a boss, no less. It plays the same, from beginning to end, just with a different colour or texture palette swiped throughout the levels. I found the game pretty repetitive, especially the arenas.
Beyond that, the story is pretty dull, though it's executed in an enjoyable style. Think a mixture of Kill Bill, Grindhouse, Lucky Number Slevin and Snatch and you've got a rough idea of it's narrative tone. Occasional clips are shown from what I can only imagine to be taken from drive-in movie ads. I don't know why, but I found them annoying... like an NYU photography student taking artsy shots of fire hydrants during their first year of school. It's just kind've hackneyed.
The final boss fight was disappointing. It's merely a button sequence action scene, as opposed to an actual fight. Enjoyable to watch, but then you just seem cheated when it's all over.
If you've downloaded the demo of Wet on Xbox Live, you're pretty much seen all that the game has to offer. If you want more of it, then by all means, rent away. I don't think it has the replayability to justify a full purchase. While I know this may seem negative, I'm hoping that I can help at least one reader save himself some money.