I've heard many good and a few bad things about "pine bark fines" for amending (tilling/digging into) soil.
First - I've heard you should only use composted or partially composted fines, as fresh can steal nitrogen and kill beneficial fungi in the soil. The only place near me, Ohio Mulch, who sells Pine Bark "fines" seems to suggest it's not composted, but I haven't called to confirm yet.
Secondly - how much acidity does it really add? While I'm not trying "per se" to acidify, a "little" acidity won't hurt, since my limestone-based soil is about a half-point more alkaline than what is ideal anyway.
Third - who has used it? Have you used it solo, or with other amendments?