svk works fine as an svn frontend. You don't even need to use the local mirroring stuff if you don't want to (though it is handy). Merge tracking (via smerge) is a godsend. I've found it's pretty smart about doing the right thing even when the other committers are using straight SVN.
The thing to keep in mind is that it's not a substitue for good repo practices. You still want branches, etc (treating your local mirror like a private branch just isn't a good idea).
I wonder if you could avoid the need to edit tags via clever use of SVN keywords & a little python string transformation?