Pros:
My guins love laying flat on it
I find it cheaper to buy fleece and wash it rather than disposable bedding
Looks pretty, you can give your cage a theme if you want
Tidier than loose bedding which spills over the sides
You won't sit down at work to find sawdust stuck to the back of your tights
I have a C&C cage and cannot leave the correx exposed because one of my guins is a chewer, so using fleece allows me to cover the sides
I found it better for long haired guins as there is no sawdust to get stuck to them
In my opinion, I would say it smells less.
Easier to notice if a guin isn't eating or has 'off' poos
Once you've made it/bought it, you don't need to buy anymore for ages - the only reason I've bought more is when I've seen some pretty fleece, not because it needed to be changed!
Cons:
You still need to use an absorbent layer underneath. I started with newspaper, but moved to bed mats, which can be expensive.
Hay gets stuck to the fleece, so you need to give it a really good shake and pat down...
... and I annoy the neighbours when I shake the fleece out the back door and the wind catches the hay and spreads it all over their garden
Poos are more visible so you'll probably find yourself doing a poo picking session every day or so
I have at least one extra washing load every week
It's more time consuming to clean the cage out
I really like the smell of sawdust, so I miss that a bit!