I don't know what planet you live on, but it's not the planet called "Reality." I have a SGSII and it has all of these great specs, but quite honestly, it's an inferior phone to the Nexus One. The Galaxy nexus and the Nexus S just blow it away.
There are so many things you can do with native android that you either can't do or are just a plain old pain in the ass compared to my nexus one.
The only things the Galaxy S II has on the N1 are internet speed (only in certain areas), camera and screen size/brightness.
Get the N1 and don't listen to spec hounds. Specs don't mean crap.
I believe you're the one that needs reality check.
A phone with extremely annoying and non-repairable touchscreen problem, faulty power button construction that makes it vulnerable and prone to failure, lousy sub-par GPU, slow USB transfer speeds, and you're suggesting it over much newer and better ones?
And to the OS argument - plain Android OS, at least till ICS, is crap - and IMHO, ICS adds nothing in exactly those areas that need adding. Any overlay will add LOTS of capabilities to it - be is crappy TouchWiz 3, much better TouchWiz 4 or also much better Sense 3/3.5. I posted enough comparisons of my own that show exactly where and how pure Android or CyanogenMod fall short and can't reach, no matter how you try.
Shortly - for the price of used or new N1, there are MUCH better options today. Sorry to disappoint.
It's not a bad phone, and some of my friends are still using it. Its quirks are livable with, if you don't demand gaming capabilities, and if you don't mind to occasionally turn off/on the screen when everything messes up, especially during navigation. If you already have it, there isn't much pressure to upgrade, if you can live with it. But if you're making your decision today - N1 is a bad decision.
And personally, neither me nor my wife found its quirks to be livable with. I lived with it for a year, because there were no better options at the time. My wife moved to another phone after 3 or 4 months.
If you want a good phone - see what fits your network. Being in Brazil, you probably need 850/1900MHz band phones, and all good MSM8x55 family models (Desire HD, Desire S, Desire Z/G2, MyTouch 4G/HTC Panache) are 900/2100 or 1700/2100 band. If some of those models exist with the bands you need - the suggestion is indeed to move to one of those. It'll be completely another world from Nexus One.