Next time I buy Samsung, people seams to be more happy about that phone.
I've now extensively used an iPhone 3, Samsung Galaxy SII, Samsung Galaxy Nexus, and Google(LG) Nexus 5.
I'd run screaming from another straight up Samsung phone, until they stop the urge to wedge a bunch of useless crap into the Android OS trying to "out-feature" other phones out there. The SII was a nightmare regarding this. If your phone requires you to run the Kies software, do not buy it. As bad as this is I'd still do this over an iPhone though, don't get me started on that one.
I was pretty happy with the Samsung Galaxy Nexus after I finally received an update that fixed a hard lockup problem - it's very stable since then and comes with none of the bloatware as Google is 100% in charge of the software. The only thing that peeved me in the end is the lack of Android updates, Google only provides updates for 18 months for it (and probably all their products). If you buy your phone some time later after it was released, don't expect any more updates. Luckily, I find that unlike with iOS, I can still run any recently made App on a pretty old Android version. My iPhone/iPod on the other hand have pretty much just been paperweights now for years because of the lack of OS/app support (once an app is updated in the app store that drops old iOS compatibility, you can't even get the old app that will still run on your old device).
What I am really happy with is my Nexus 5. It's fast, great screen, never locks up, no bloatware crap, really good battery, and it's very cheap for what you get. Unless there is some specific need you have that some other phone might handle better (better camera, waterproof, etc.,) I think you'd have to be a bit nuts not to take a good look at this device.
