I have a love/hate relationship with blocks. I LOVE the collaboration they inspire. I LOVE the problem solving and critical thinking skills they encourage. I LOVE the rich imaginative dialogue that accompanies their use. I LOVE the way blocks are "age appropriate" for any person.
I HATE that we don't have enough class time to truly develop the stories/themes/structures that the students need to create. I HATE the way the blocks spread all over the room, causing clumsy people (ME) to stumble and trip. I HATE the way the blocks invite the students to throw them."But I'm cleaning them up, Mrs. Dyer! I'm just trying to make it into the box." I had to come up with an uber specific rule about blocks and throwing. Simply saying, "Don't throw blocks" isn't enough. No, I have to say, "You may not throw the blocks. You may not throw them even if you're cleaning up. The block can never be airborne. The block must be touch either your hand, another block, or the floor AT ALL TIMES."
But honestly, blocks are wonderful. Their benefits far outweigh the few headaches.