The interesting thing about the "compatible" capsules is if you read the reviews on Amazon, on average there are four people who rave about how great they are for every one person who says they can't believe how horrible this stuff tastes.
How something tastes is very subjective, and the only way to know for sure is to try it out yourself and see. But the compatibles sell for as low as .32 per capsule, while the Nespresso brands sell for .70 and up, so it's worth giving it a try if you're going to drink a lot of espresso.
Espresso purists would never put milk, cream or sugar in their beverages. For those people, maybe the Nespresso brand really makes a difference. For the rest of us, I think we're not that sensitive to the subtle differences between brands. After all, this stuff is not rocket science. They grind coffee and put it in a capsule. I don't think Nespresso has some unique technology that makes them so much better than everyone else. I think it's mostly marketing in my opinion.