"Intuitive gestures, meet responsive UI."4.5 starson by Invalid-Username
Pros: Very smooth and beautiful UI
Blackberry hub aggregates your life!
Best soft keyboard in existance
Very cool lockscreen
Best mobile multitasking
Tons of RAM (2GB)!
Expandable storage (up to 64gb)
Cons: Apps (though most of the major ones are there or coming)
Mapping solution isn't as comprehensive as Goole Maps
Delayed US launch (thought that might be the carriers' fault, it will impact consumers regardless)
Summary: Having used an iPhone from 2007-2009 and 2012, WebOS from 2009-2010, and Android from 2011-2012, and now finally the Z10 in 2013, I can say that I have quite a bit of experience with mobile operating systems. I was probably one of Blackberry's biggest detractors. If you had asked me what I thought of the Z10 a year ago, I would've said that Blackberry wouldn't even make it far enough to launch the device. Well, now that I've had the device (imported it and unlocked it since carriers won't have it till March), I can tell you that it is a great phone! I'm very impressed with what BB has done. The visuals in the OS are absolutely gorgeous (TAT acquisition was definitely worth it!). The OS is super smooth (smoother than my Nexus 4. On par with iOS, with a smoother keyboard). The keyboard is top notch. Instead of rewriting all these things, just take a look at the "Pros" I've listed.
Overall, this is probably the best smartphone I have ever used. Sure, I'd love to see a few more apps, but I have no doubt that the majority of big name apps will be here shortly (Skype is confirmed, Whatsapp is confirmed, Yelp, Instagram will probably be there, etc.).
I think long term users of Android/iOS will absolutely love this phone if they keep an open mind (fanboys, keep worshipping your OS deities; this phone isn't for you) and take the time to learn all the gestures that make this OS so intuitive.