I've had mine for about 6 weeks, it's slowed down a bit a couple of times, just waited 10 seconds and it works again. It's frozen once where I needed to remove the battery, it was whilst trying to refresh a webpage, went faded as if a message was popping up, and nothing happened.
Other than that I love it though, it's a great phone. But having come from non smart-phones I've nothing to compare to, so obviously I'm going by the improvement in web browsing and stuff.
I'm on Vodafone by the way, but you can choose the standby theme and I didn't like the Vodafone one so I'm using the SE one.