In Florida it is illegal to use the term 'Engineer' or derivatives in a business name if there are no licensed professional engineers working there. There may be restrictions on using the term even if the number of licensed engineers working there is not zero, but if there are zero you can't use it.
Realistically, there's no reason to call yourself an 'engineer'. At least in the US, because of restrictions similar to the one above the term 'Engineering Services' or similar is limited mainly to the architectural firms you mentioned. The term is co-opted. Just call yourself a consumer electronics designer, embedded software developer, analog electronics designer, digital designer or whatever is more specific to your case.
As for whether it would ever be worth it for an electronics engineer I've found the answer is generally no. I've worked for several different companies in different fields and no one even gave it a thought. It wasn't expected, it wasn't sought and there wouldn't be talk of a raise or anything if you did get one.
I only ever really hear of two types of electrical/electronics/embedded engineers getting the PE: engineers who have years of experience in a variety of areas and had a specific need in mind when getting it and confused new graduates who have been talking to their uncle who's a civil engineer.
Edit: After skulking around on Wikipedia for a bit I've unearthed some information that is interesting but doesn't change my original answer. That is, this information applies only to other circumstances.
It seems that the restriction on using the term 'engineer' is more directed towards not being allowed to offer the public 'engineering services' unless you or your company is licensed. Thus saying 'Hi Bill, I'm Fred and I'd like to offer you engineering services in exchange for money - here's my card' means you need to be a professional engineer. If you're just a shmo who works for a company you can put 'engineer' on your business card because you're not offering any services to the public - your company is doing the offering and hopefully they have this mess sorted out for themselves.