New Zealand Electorate Map

I have been developing a Google map mashup on New Zealand Election 2008. The election map below is 100% accurate boundaries data(data from www.stats.govt.nz), which contains 63 general electorates and 7 Maori electorates.This map widget helps voters figuring out which electorate they belong to by ticking the electorates and will be used for the election section of www.stuff.co.nz.

After researching some different methods of visualizing the data, the most reliable method utilises is Javascript with the Google Maps API , and Keyhole Mark-up Language (KML) to create a thematic map of the regions. There are a few limitations. Large KML files don't load in Google Maps, medium-sized files load very slowly—it seems Google is parsing the KML using Javascript.
Here is an example Australia 2007 Election, which takes 14.31 seconds, a significant initial loading time.