Here's Mark Russinovich's review's conclusion about Vista SP1 File Copy Improvements:
The changes apply both to Explorer copies as well as to ones initiated by applications using the CopyFileEx API and you’ll see the biggest improvements over older versions of Windows when copying files on high-latency, high-bandwidth networks where the large I/Os, SMB2’s I/O pipelining, and Vista’s TCP/IP stack receive-window auto-tuning can literally deliver what would be a ten minute copy on Windows XP or Server 2003 in one minute. Pretty cool.
Some of you will probably see this review as too much soft for Vista's copy problem, but you'll have to understand, Mark is now a Microsoft employee. Still a technical authority, though.