Yes, old hardware will always fare poorly when running operating systems that are generations ahead. Try running Windows 7 on a 286... Nexus 4 and I'm loving it. I anticipate no issues moving between 4.3 and 4.4.
Oh, and I suspect your battery is torched. my wi-fi only nexus s reports on average a solid day of battery with moderate/heavy use.
To be fair, that was during the iPhone 4 period.
The iPhone has since gone to the iPhone 4s, iPhone 5, and then iPhone 5s. Many users report an absolutely miserable experience with iOS 7 (and even 6) on the iPhone 4.
The mobile industry has moved very, very quickly, and devices are a magnitude more powerful+ than just a couple of years ago. As a developer with an interest in mobile, I've gone through literally seven different smartphone devices in the past three years.
It removes the 'fly in' 'fly out' animations for opening folders or apps, and greatly improves performance.
Same for the iPad mini.
I experienced the nexus 4 a little bit and though it's a great phone I'm afraid the next OS updates are going to ruin it just like it happened to the poor Nexus S.
My next phone is going to be an iPhone as I had a rather pleasant experience on the iPad.