home depots lumber doesn't look pressure treated to me. i asked about it once and they told me it's a new method that doesn't use as dangerous/toxic a type of chemical.
but what i notice is i can almost point out what lumber i got from home depot and lowes. it may just be appearance, but the lowes lumber looks like it is holding up better. i got to where the only reason i went to home depot for lumber is that they were willing to cut it to lenth if i needed it, and they seemed to have more sizes in stock.