I really loved The Mars Volta's previous album, De-loused in the Comatorium and I was rather uncertain when I first heard this. It certainly wasn't as easy to get into than their first one but after you've had the patience to listen to it a few times it all starts to make sense.
On this album they've incorporated a lot more instruments and styles to the music and at the same time gone even more crazy in how they use them. Generally this works really well and the use of Spainish lyrics (at least I think it's Spainish) sounds really good, and it's not like their lyrics made any sense anyway... The track listing is as crazy as the music and you get the sense that they added in breaks between tracks on the CD just as a courtesy.
My main complaint would be that sometimes they go a bit too far and venture into the realm of randomness. Four minutes of the same piece of birdsong played over and over again can become tedious very quickly so I just skip past it.
All in all it's a really great album and something completely different. It's worth getting just for the last track alone. It's not for everyone though, I could understand how some people could hate this. If you haven't listened to the Mars Volta before I would recomend their first album over this as it's a lot easier to get into.