Are you sure you aren't thinking about the original Galaxy S2? The Skyrocket got a CPU upgrade along with LTE support, and it definitely wasn't a PoS. My wife and I finally upgraded when the batteries stopped holding much of a charge, but I keep them around and they are still reasonable devices. We certainly never had a problem with not being able to answer a call, or apps taking too long to load.
I have one on Sultan's old KK ROM and the other I'm using as a test-bed for Candy6. I will admit that LP and MM have been poky on these old phones, but hell, they are 5 years old at this point. That's an awfully good run for any device.