[Tilesathome] Purpose of Tiles at home

[Hans F. Nordhaug]

Hi!

Not long ago I set up a server to participate in the Tiles at home
project. I Twittered it and the following disuscussion took place:

----

Me: I have just installed the Tiles at home client on my server - nice to be
able to contribute some CPU cycles to the OpenStreetMap project.

Shaun McDonald: um do you know that one machine can deal with the
rendering of the whole world wilst T at H needs lots of machines and
bandwidth?

Me: Yes, but until that machine is up and running, we need to keep the
rendering queue down... Are you offering such a machine for OSM?

Shaun McDonald: Take a look at the default map on the osm.org website,
it is already is using the diffs, up to 10 minute delay depending on
load

Ref

http://twitter.com/hansfn/statuses/4175284365
http://twitter.com/smsm1/statuses/4314776666
http://twitter.com/hansfn/statuses/4325706671
http://twitter.com/smsm1/statuses/4326127392

----

OK, I did some testing and Shaun (who is a "Junior Developer" at
CloudMade) was right - the map was indeed updated in 10 minutes or less.
(It works perfectly most of the time.)

So what exactly are we contributing to when we participate in the 
Tiles at home project? 

Regards,
Hans

PS! http://www.informationfreeway.org/ says that Mapnik is updated
weekly. Is that still correct?