Reliability of old iMacs?

Generally reliable however remember it is almost 8 years old, the parts that are likely to fail are moving parts such as hard drives, DVD drives etc. Personally I'd stay away from a computer that old, it has extremely limited use. If you are trying to save money then buy either an Apple refurbished model or some places such as OWC (www.macsales.com) sell used Macs that have at least some warranty.

 

Is this the polycarbonate/plastic iMac or the first generation aluminum that followed it? If it's the former, I don't think you'll be able to run OS X past 10.7, which means that you won't get the most recent security updates. It also depends on the requirements of the apps that your kids will need to run for school. You may want to consider a newer used or refurbished iMac instead.

 

My CD2 alu iMac is still going strong after over 7 years, and apparently (& surprisingly) is supported for Yosemite.
I replaced the hard drive recently after it failed (first time) and its still going strong running Mavericks.
I think a good example for £150 would be well worth a punt, provided its the aluminum version (mid 2007). Be prepared to put more ram in though.

 

I personally would not bother with C2D iMacs, because iMacs hold their value so well, the older ones aren't that great in terms of value for money.

I'd be looking at somewhere around the 2011 range when they used the desktop class sandy bridge processors and AMD Radeon HD graphics. The good thing about these models are that they have easily upgradeable RAM, they can run the latest OSX, and they have an unused SATA port on the logic board if you ever want to upgrade or add an SSD.

In addition, the Core i5/i7 CPUs used in these models are exponentially faster than the C2D CPUs, since they are all quad core with turbo boost.

 

I just bought a second hand iMac 2008 24' screen c2d 2.8 4gm ram 320gb hdd, the reason i bought because the seller kept it very nicely with all the original packing included and the condition is nearly perfect, and the price is reasonable (around USD400)

I actually have the first rmbp 15" but most of the time i use it in office so i decided to buy a iMac at home just for internet browsing and checking email and i think USD430 is a good deal to get a perfect condition iMac even though its nearly 6 years old. Now I have owned it for 2 weeks and I can say it is joy to use this machine on a lot of things..like watching back my DVD and the very big screen for internet browsing...(something i did not expect its the speaker on iMac is really good...better then my cheap 2.1 speaker) , just hope the machine will run for few more years and i really satisfied with it...i also just installed league of legend on it and it also runs perfectly..