I would imagine that it would generally be incompatible.
It depends on your package really. For eg, i use the 2k8 bids and then test my packages on 2k5. I have never had a problem, BUT i always run/deploy through 2k5. If the package uses some 2k8 functionality that is not available or supported under 2k5, then it would fail.
Out of curiosity, why dont you just use 2k5 integration services?
Adam Zacks-------------------------------------------Be Nice, Or Leave