WCNG - Upgrading working copies

Hi,

I'm currently trialling the nightly builds that Stefan is providing for
TSVN, which include the new WCNG implementation. So far, it all looks good.
It takes a few minutes extra to checkout a working copy, but the day-to-day
performance difference (to me) is not noticeable. Good stuff!

One thing I did notice, though, is the performance of the 'svn upgrade'
functionality. It seems to take, on average, 3x longer to upgrade an
existing working copy than to just delete and checkout again.

Checkout (1.6.x): 9 minutes
Checkout (1.7.x): 14 minutes
Upgrade (1.7.x): 43 minutes

Is this kind of performance hit during an upgrade expected? Is the
recommended upgrade option expected to be to use 'svn upgrade' or do get a
fresh checkout?

If you need stats regarding the working copy, I can provide them.

Cheers,

---
Daniel Becroft