well, I have the Bondi Blue 233MHz and it has impressed me with its build quality. It just keeps working even tho' it has been hit by lightning once ( and required a new modem). It is quite slow - it handles a maximum of 256Mb SO-DIMM PC100, some 233 iMacs handle more - but when I put a 128 and a 256 SO-DIMM in mine, it only recognised 128+128Mb. I upped the HDD to 40GB but remember that you have to keep the first boot partition below a critical size ( I think I chose 7.5Gb). I was able to put 10.2.8 on it directly, as there is no DVD option nor Firewire, so it's very hard to get to 10.3 (I did happily run with 10.3 having installed this on my HDD in a PowerMac - then put the HDD inside the iMac) I never tried 10.4.
So its a slow, reliable, CD only , USB1 only , non FW iMac with 4 or 6 or 8Meg of VRAM. I'm keeping mine!!! I'd suggest that the minimum Mac to try and find nowadays is the next generation - Slot Loading iMac, particularly iMac DVSE with FW400 and no cooling fans - I'm typing this on my Graphite iMac with 0,5GB Ram and 120GB HDD. it's not quite as "bombproof" as the 233MHz but also fun!
enjoy!