Any point in waiting for the SHA-3 standard? The Wikipedia article on SHA-3 says that Keccak has been chosen but the standard hasn't been issued. Does this matter? 

That is, can we just assume it's going to be as specified by the submitters (specifically for SHA-3-256 it's the Keccak-f-1600 permutation, in a sponge construction with r=1088 and c=512 and the pad10*1 rule)? Or might NIST wind up tweaking something, meaning we might have to re-hash a bunch of things if we made this assumption -- which, depending on application, could be inconvenient.

(EDIT: of course, waiting is also inconvenient, thus there is a risk-benefit question here -- again, depending on application.)
From John Kelsey on the NIST mailing list for SHA-3 (http://cio.nist.gov/esd/emaildir/lists/hash-forum/msg02656.html if you are on it — it's password-protected):

a.  We plan to allow the collision and preimage resistance to be the same for SHA3, since that fits with the notion of a single security level, and since that will substantially improve hashing performance.  That is, for a security level of 256 bits, we can accept a capacity of 512 bits, representing both collision and preimage attacks of $2 ^ {256}$ work.
b.  We plan to allow the variable-length feature of Keccak by default, since it seems like such a useful feature.
c.  We are considering whether it makes sense to have many different capacities or only one or two.

So short answer, they do seem set to lower the required capacity from the initial proposal so it isn't as dog slow in software, but haven't figured out what the exact settings will be.