<p>I've been having a hard time lately getting the raft off of my ABS prints.</p>

<p>Is that a symptom of either a nozzle or bed that are too hot? Or is there some other factor I should be looking in to?</p>

<p>I have an UP mini that I've modified both the nozzle and bed to customize the temperatures on.</p>

<p>Bed gets heated to 100˚C and nozzle is either 266˚C for UP ABS filament or 236˚C for off-brand ABS filament.</p>

A couple things to consider:
Ensure that your build plate is flat and level. An un-parallel HBP could result in the object "welding" to the raft.
Turn down your nozzle temperature. It is likely that the material is hotter than it needs as it is extruding. This results in a slower "cool-down rate". So, if it takes longer for the filament to cool between the raft and the first layers of the object. Therefore, cooling together in a manner that somewhat binds them.
Personally, 266C seems VERY high to me. I've primarily only used ABS on my MakerBot and have successfully printed with 225C +-5C nozzle temperature and 110C +-2C HBP temperature.
Typically you want to extrude slightly above the melting point. You don't want to liquefy the material, but make it pliable enough to bond it to other layers of material (or a BP).