There will come a time when you have to set the hammer down, and it's always safer to use the decocker. Being a lefty, it will be a pain in the ass to do this, I tried it with my Smith a few times and it was difficult.
As far as taking care of it, I'm sure you take care of them (I'd hope so), but stainless is just that much easier to take care of. I've always been more worried about my blued/parked guns, but the 5906 was always at the back of the list, cause it didn't care.
All the same, I'd go under 500. There's one on GB right now which would be about 450 after fees, in the same condition, minus the box, but I don't need that. If you can shop around and find a 459, it'll be about half the price too, maybe 3-350 and will give you the same good service, and may even have the ambi decocker. I think it's a cool gun too, but you don't want to get struck by the gun love bug and then regret the decision (you overpaid a bit for that 4506 and I'd be a dick not to advise you on this next purchase).
I just looked on their site and they have a 5906 on there too, with the adjustable sights and the squared trigger guard, for 10 bucks less. As an everyday shooting gun, that will fair better. If you decide against that, I might go for it myself.
http://www.collectorsfirearms.com/ad...p?itemID=36572
5906