I understand that this thread is a little old, but ... I found it, so someone else is likely to find it. This is not necessarily the solution that I know, and what I have experienced in the past and most recently.
I studied this question for a long time. We are suffering from the same problem. Sluggish response time on Windows workstations + Linux web servers with SMB shares that host each user check.
The time taken to commit / update / request is terrible. We all just learned to live with him because of how our development environments are defined. They are all semi-remote, not on our local machines, which is sad for developers, but how did the security officer and system administrator do things back when.
To be fair and not blame it all on TortoiseSVN, we had problems with sluggish response times in other applications. I personally experience terrible delays when editing any code in my checks using Eclipse.
TortoiseSVN seems to have added some information to its FAQs since I last looked (forever):
Can I create a local repository in a network directory? http://tortoisesvn.tigris.org/faq.html#repoonshare
Can I save my repository on a network resource instead of setting up a server? http://tortoisesvn.tigris.org/faq.html#reponoserver