After writing my last post I decide to install the Koala onto my SSD, replacing Mint 7 in the process.
It was hard saying goodbye to Mint 7 as it had been a rock solid distro and it is still the distro that I would recommend to new users. The Koala's Eee 900 compatibility was just to good to pass up, however, and after warning the missus that it was all going to change, I went ahead with the install.
The install went without incident and, not surprisingly, my boot time has been reduced from approximately two and a half minutes to approximately forty seconds.
I did mention that I had seen forum posts from other 900 users who were having shorter boot times than mine and it appears that all of those users had installed to SSD rather than SDHC as I did.
A quick perusal of the Ubuntu forums pretty much confirmed that users who install to SDHC are suffering extremely long boot times. But it seems to be a bit of a mystery as to quite what's going on to cause this.