Ok let's get down to brass tacks, shall we?
I don't like Motorola phones...I don't hate them but I don't like them. It's 75% Motoblur, 15% screen, and 10% of being slightly unfamiliar with how things are laid out compared to Samsung. NOW....the new Motoblur for the D3 and Bionic is actually great and leads me to overlook the bleaker looking screen (compared to the SAMOLED). I'm a pretty well balanced appreciator of smartphones. I'm 50/50 when it comes to simple aesthetics and functionality.
The amount of lag and stutter found with an out-of-the-box Charge is small enough that it only affects the aesthetic aspect of the phone for me and never have I felt that it was a poorly fucntional device. When rooted and properly ROMed (not overhyped or overclocked) the Charge is probably the best single-core device out there to date, and overall, better than most current dual core devices.
The Bionic is cool, but the problem now is that we're not too far away from having truly next-generation devices. Where as the Thunderbolt, Charge and Revolution were considered "last year spec" devices, what made them next generation was that they were super-fast LTE phones. Even if the Bionic came out 3 months ago, it would've helped it feel like something special...like the bridge between yesterday and tomorrow. Even with its fantastic specs, the Bionic now feels like the period at the end of the first LTE sentence, and not the transitional statement that it should have been.
And in terms of speed and smoothness of (at least) the UI, few Android phones (single or dual core) are going to be as smooth and snappy as an iPhone or even a Windows 7 phone, due to the lack of hardware integration. The true test of smoothness is not how well it looks when you zip back and forth from homescreen to homescreen, or how quickly you can get your notification bar down, it's how smooth it is when you very slowly slide from homescreen to homescreen and slowly pull the notification bar down. When there is absolutely no stutter or unnatural feel to the movement is when you're cooking with Crisco!
Supposedly the GS2 has hardware integration of the UI, but I will never find out or care, for that matter, because VZW ain't getting it. Hopefully future devices will follow suit.