Upper Levels What are the pros and cons of upper levels?

Our cage has an upper level that I just opened up to the GPs today. I had no idea whether they would use it or not. I put a grape in the lower end of the tunnel, and went to the grocery store. When I got back, the upper level had aspen on the fleece, indicating that someone had been up there. I put out two halves of a grape, one at either end of the tunnel, and within three minutes, both GPs were on top. They've been running up and down madly all afternoon.

My boys' favorite spot is up top, because I don't have coroplast on the side facing the inside of the cage, and they have a better view of what's going on from there. They are confident fellows and seem to find the antics of my son and my dogs amusing.

The ramp in my design is only about 7" long and they don't mind it at all. (There are photos in my gallery.)

I like having hay on the upper level. When I had hay on the main level, no matter how hard I try to keep the hay contained in one area, my pigs will always find a way to drag them around the cage. Once I put hay on top, I don't have to clean hay and litter from fleece anymore. Not a single strand of hay on the bottom level.

I set up my C&C when we first got our guinea pigs 3 months ago. I liked the idea of having the litter box and all the hay away from the play area. It's especially nice since I have changed to fleece. All the messy stuff stays upstairs while the play area is nice and clean. I have fleece upstairs also, but it's much smaller so cleaning off the hay not a huge task.

I made a second level because I wanted to expand my cage, but I didn't have the room to go any other way. I have a wire shelf lid with blankets, beds and toys on top for my 3 cats and they love being on top of the guinea pig cage.

I made my ramp out of 3 mesh grids over lapped by 1/4 so it's around 2 and a half grids long, with fleece on it to protect the guinea pigs' toes. My guinea pigs almost immediately ran up the ramp when I put them back in the cage after I added the second level, but it took them a while to learn how to get back down. lol

I have just recently removed the top level of my girls' cage as I needed a few more grids to make up a large cage for the two boys staying with me. The younger of my two girls Avril seemed to like the upper level and would tear up and down the ramp sometimes when she as in one of racing moods. The older girl Buffy didn't care for it too much and would go up there to eat and that was it. I think she is enjoying having the 'kitchen' at floor level now haha lazy pig. It is also less 'exposed' for her I think and she doesn't go racing away when I walk past if she is eating which surprised me she is usually quite easily alarmed.
Im not sure I will put the top level back in, the 2 girls have a 5x2 as it is, and seem pretty content with it. It is also good to have a more 'moveable' c&c cage. With the top level in it was a real mission to move it anywhere, unless I wanted to cut the cable ties and remove the whole top level first. but now I can just fold all the sides up and easily relocate it.
It was easier to clean the 'kitchen' though when it was a seperate level, so really it's down to your own preference (and what suits your guinea pigs)

I have had my cage both ways. Before I split my herd of 4 into pairs, they shared a 3x5 with an upper deck. The pros:

It was easiest to keep hay,etc, of the bedding on the main level. My upper deck was the "kitchen".
More variety in space for the pigs. Mine never had a problem navigating the ramp, and genuinely seemed to enjoy it.

The major cons:
The ramp will usually take up SOME space on the inside of the cage, which takes away from overall floor space.
It CAN be harder to clean under the deck (depending on your design).

Now we have a 2 level cage, but each level is its own cage (two cages, but stacked like bunk beds.) They don't seem to notice the absence of the upper deck.