My school's technology club uses, almost exclusively, six or seven year old Dell Optiplex computers (because they're what we have, and we don't have the money or resources to get new or better things). All of those computers are running 10.10 perfectly fine.
We don't have any tricks up our sleeves, we just did a basic install. Sure, they've been tweaked a little (they're using Nautilus Elementary instead of plain nautilus, and the Mint Menu + DockbarX instead of the default panels, but they're almost a vanilla 10.10 install).
Thus far, we've yet to have any problems with them. Last year we had them running 9.04 (a couple got an upgrade to 9.10, and one got an upgrade to 10.10). They all work fine. Before that, they were running Windows or various other distributions (we've even got some of the old disks). We've never had any problems with the "old" hardware.
The only difference between those computers and my own computer are that they're running 32-bit, and don't have all the applications I use.