I'm also a fan of tiered prizes ... and although it's fun to see how 'out there' you can get with the prizes, I honestly don't like the idea of making partners go a great deal out of their way to access them. I also like to give them the option of a cash equivalent if they don't like what's being offered.
I prefer guilty pleasures that you might think are cool to have, but you'd never actually go out and buy it ... or at least it wouldn't be high on your list of priorities.