I was just looking at craigslist and under farm/garden there's someone who will deliver a load of hazelnut shell mulch for $100 in Portland metro. Doesn't say how big "a load" is.

The ad says it's good for keeping snails and slugs out. Are there any reasons not to use these shells as mulch?

In regard to the pros and cons - I use them in paths - they don't track around like other mulches. You can't walk on them barefoot.

Squirrels do love to sort them - you should get them spread as soon as you get them otherwise the squirrels will make a bit of a mess. I have found the hulls migrating around the garden based on squirrels, but it's not a big deal for me.

They smell a little funky when wet, but it's not terrible and it goes away. I might think twice about putting them under a window.

And they can be a little expensive based on your locale - but they last forever.