Some peat mosses use a chemical to make them water asorbing; peat when completly dry, actually sheds water. Untreated peat can take AGES before it gets to a point where it has enough moisture to get hydrophilic. And there is the acidity thing S&S was talking about; I used to use untreated peat to filter water for my angelfish (who are Amazonian and like a pH around 5, kind of sour if you like your veggies sweet)...you can move a soil into the 4 range with too much peat...
I use coconut coir instead; it's getting easier to find, it's ph neutral and the compressed blocks I buy (from my friend Petie at Perennial Harmony but you can find it online as well) maybe a foot long and 4x4 in., blow up to fill a regular wheelbarrow (and a lot faster than organic peat will soak up the water (chop, spray, mix, leave it for a bit, repeat until uniformly broken up)
PLUS it's a waste product of coconut production, while peat is a non-sustainable mined product (if you start a peat bog today it will be ready for harvest in a couple of hundred years). So its greener too