They all get kind of warm, but none were uncomfortable or disconcerting to me, certainly not compared to modern machines.
The 100 series used squishy thermal transfer pads mushed against the keyboards as heat spreaders (when they used heat spreaders), where the 200 series usually had a fairly large flat metal heat spreader. So, the 270 may have had more effective heat distribution than the 180. Or, your 180's thermal pads may have disintegrated over time.
I've had the rubber feet on mine stick to stuff without the computer running. That ancient rubbery stuff tends to turn to glue.
The 5300s I disassembled either had no thermal compound, or very old thermal compound, so I put new stuff on there before I put them back together. The 1400s used some squishy stuff between the processor and heatsink, as did the 2400 and (I think) the Kanga. The 3400 either had no thermal compound, or it used squishy stuff. The WallStreet started using thermal compound between the processor and that little round cap thing, and then squishy stuff on the larger heat spreader. I forget what the original iBooks used. The TiBooks started using some weird stuff that kind of melted and adhered the processor to the heat spreader. iceBooks kept using squishy stuff. AlBooks use regular thermal paste on both the processor and GPU. I don't remember what the iBook G4s used, either the melty junk or regular paste.
The 100 series used squishy thermal transfer pads mushed against the keyboards as heat spreaders (when they used heat spreaders), where the 200 series usually had a fairly large flat metal heat spreader. So, the 270 may have had more effective heat distribution than the 180. Or, your 180's thermal pads may have disintegrated over time.
I've had the rubber feet on mine stick to stuff without the computer running. That ancient rubbery stuff tends to turn to glue.
The 5300s I disassembled either had no thermal compound, or very old thermal compound, so I put new stuff on there before I put them back together. The 1400s used some squishy stuff between the processor and heatsink, as did the 2400 and (I think) the Kanga. The 3400 either had no thermal compound, or it used squishy stuff. The WallStreet started using thermal compound between the processor and that little round cap thing, and then squishy stuff on the larger heat spreader. I forget what the original iBooks used. The TiBooks started using some weird stuff that kind of melted and adhered the processor to the heat spreader. iceBooks kept using squishy stuff. AlBooks use regular thermal paste on both the processor and GPU. I don't remember what the iBook G4s used, either the melty junk or regular paste.