Congrats!
On your local Windows machine, did you have to edit anything?
This is what I had to do, and I`m not 100% sure that step 5 is needed:
1. In Windows, in Putty's PuttyGen tool, create a new public and private key pair. (TODO: identify optimal settings)
2. Ssh into server and vi ~/.ssh/authorized_keys . See VI cheat sheet. 
3. Using Shiro's syntax, enter your public key:
Code:
command="~/bin/svnserve -t" ssh-rsa [key omitted]
4. Repeat 1-3 to make a new key that you can use for regular ssh syntax.
5. On your Windows computer, edit C:\User\Username\AppData\Roaming\Subversion\config. In the [tunnels] section, add this on a new line:
Code:
ssh=C:\\Program\ Files\ \(x86\)\\PuTTY\\plink.exe -ssh -i C:/SomePath/private.ppk
Question: is this step necessary?
3. Start Pageant from Putty and click "Add Key." Pick the same private key as above. It'll ask you for the passphrase for this private key, so enter it. This private key corresponds to the public key on the server
4. TortoiseSVN can now fully interact with the server.
Question: Are you using Pageant from the Putty package to manage your keys? You mentioned using Putty. Is that only for interactive ssh shells or does TortoiseSVN pay attention to settings make in Putty?
Question: A window containing plink.exe jumps up obnoxiously whenever I use TortoiseSVN. Anyone else getting this? How can I get rid of it?
Notes:
* On the server, in ~/.ssh/authenticated_keys, you can specify the absolute path of svnserve ( /home1/username/bin/svnserve ) or relative ( ~/bin/svnserve)
* The order you specify your keys in ~/.ssh/authenticated_keys does not seem to matter.
** I have a sneaking suspicion that putting the one you use most frequently first in the list will make your experience faster.
* In Windows, using Putty's Pageant, you can specify multiple keys.
** The order your specify your keys in Pageant doesn't seem to matter. I have a sneaking suspicion that putting the one you use most frequently first in the list will make your experience faster.
** If they happen to have the same passphrase in multiple keys, Pageant will try to use the same passphrase, so in theory you only have to enter it once for many keys.
*** Years ago, I spoke with the Pageant developers about this being a security hole, but they (correctly) defended that it's not a hole, rather it's a convenience.
*** This came up years ago when I did open source development on multiple projects; perhaps this is not appropriate for more secure work.