I have been monitoring the Raspberry Pi running apache2, php5, mysql powering a wordpress blog under very low traffic. I have noticed the load times are very unreasonable, with every page load causing a 100% spike in cpu activity for a fair period of time.
As can be seen in the above graph load times were very extreme considering the device was solely used just for running wordpress and the related software.
Frequently the raspberry pi would become completely unresponsive even to SSH connections.
Obviously a low powered device like this simply cant handle the standard software's demands. Mathew Shadel's blog http://matthewshadel.com/raspberry-pi-webserver/ talks about some interesting ways minimalise the software load with different software, I may try this in the future but for now I want to try a few different things with my Pi and not have it tied up in a server room.
Just a heads up, there is a clone of this very blog running at http://blog.lachlanmiskin.com on a Raspberry Pi.
It is running the standard Debian install provided at the Raspberry Pi website running stock standard apache2/php5/mysql server. This is very heavy for the low powered Raspberry Pi so if your trying it out, expect very slow load times and occasional crashes. From my experiences it seems that with an overload will cause the whole system to become unresponsive and requires a power cycle.
There are other software packages around for lower powered linux servers which I may look in to sometime in the future.
I recently received an MK802, so who knows may the blog will be dished out from that eventually.