There's nothing wrong with making everything into an object, in fact there's a lot to be said for it. I've found that most maintainance headaches have arisen when the code is some bastardized mixture of OO and procedural code.

I'm not sure what you mean by 'nested objects'. If you mean using delegation then I have to disagree, delegation is often a great way of getting well factored loosely coupled code with a minimum of dependencies. If you're talking about deep inheritance hierarchies (complete with the added fun of multiple inheritance) then yes, you have to be bloody careful with it.

The thing about OO is that you have to do it wholeheartedly OO code can look somewhat... 'diffuse' to someone who is used to the procedural way of doing things and it can be hard to see where stuff actually gets done, but careful method naming combined with well 'composed' methods alleviate that. Especially when you've got a test suite to look at too...