A note about chargers and mAh ratings. My source is the Battery University:
http://www.batteryuniversity.com/partone-12.htm
They recommend for small batteries like cell phone batteries to charge them at less than "1C" (for the Nexus One that would be less than 1.4Amps or 1400mAmps) so these chargers should all be fine.
They mention that charging at higher currents can cause the battery to get hotter. Heat shortens the eventual lifespan of a Lithium Ion battery so "bigger" is not necessarily "better" in terms of chargers. A lighter charge can be gentler on the battery than a beefy charger.
They also mention that higher currents do not shorten the charge cycle by much. At higher currents the battery electronics typically kick the charge cycle into the "topping charge" state earlier and since the topping charge is very slow, it takes longer to get to 100% charge. A lighter charger may take longer to reach the end of the initial regular charge cycle, but it will turn over into the topping charge state much closer to full. Thus, a stronger charger will get you to the topping charge state (i.e. mostly full) quicker, but take almost the same amount of time to get to the really 100% full state.
I typically use a Blackberry charger on my phones - they tend to charge at lower amperage and so induce less heat. I also charge them overnight so even if the charge was slower it wouldn't really matter because 6-8 hours is plenty for any charger to get these phones to 100%, but likely the lighter charging isn't really taking much longer anyway. If I desperately needed to get my phone charged up very quickly during the day then I would definitely use the stock charger or a charger that was stronger, but still under the 1.4Amp maximum recommended current - but if you charge overnight, try using a lower amperage charger for long term battery health...
