In the first version, the chair would make them nap about 95% of the time. Since the .05 update it takes FOREVER to get the nap option to come up, so I began to praise mine any time I see one of them do it, from anywhere in the house (even when I don't actually let them nap at that time.) That seems to make it a little faster to come up when I DO want them to nap. The chair always seemed easier than the sofas, even in the first version the sofas seemed to trigger watching tv more than taking a nap. Regardless, I have to say I still do believe the chair and sofas are hotspots for nap taking.
I also agree that nap taking is much more effective at short term energy regeneration than going to bed. Going to bed is only effective if you are going to close the family and not open it again for several hours. In other words, it's really better to let them do it on their own (in my experience, at least.)
Edit: I never noticed any use for the hammock whatsoever, in either version of the game. Although there was much talk of it being helpful for the tired/exhausted issues with the first version of the game here on the forums, I never noticed any increase in energy levels of any of my lil peeps who used it. That has not changed with version .05.