truecrypt and defragmentation

Hi all
I've read various (old) threads here and elsewhere (including Truecrypt's own guide of course), but I'm still uncertain, so I'd be grateful for anyone's experiences when using a defragmentation tool (I would probably use Auslogic's freeware one) on a truecrypt encrypted system volume.
Has anyone experienced problems with this?
Has the fact that the system volume is encrypted got in the way of defragmentation making the process extremely lengthy (as suggested here:
http://serverfault.com/questions/21097/defrag-a-drive-encrypted-with-whole-drive-encryption )?
Truecrypt's own guide refers only to the security implications of defragmentation, which I can take on board, but it doesn't actually state whether it is advisable or inadvisable from the system's point of view or even whether defragmenting an encrypted drive is a worthwhile thing to do (ie does the process of encryption actually result in a situation where defragging would have little impact on the speed of the system when all is said and done?)
Thanks
David