Did you jailbreak it back in the iOS4 days? If you did, then, it's possible to downgrade it to any iOS version you've jailbroken it under.
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The iPad2 is the only A5+-based device that can be downgraded, assuming it was jailbroken back in the iOS4 times.
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... if it DID stabilize, that is. For example, the iPhone4 is still sometimes (for example, opening the dialer) three(!) times slower under the final version of iOS7 than under iOS6.
"Nice" work, Apple...
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My iPhone 4
... and have fun having a still fast device, and not a laggy one ...
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A lot of people rightfully hate the, for a given device model, last-available iOS versions. Many models have been (intentionally?) crippled by the last major iOS version released for it - the iPhone 3G, the iPod touch 2G, the iPhone 4, the iPad 1 etc. No wonder people are afraid of upgrading "old" hardware. No one wants an expensive paperweight.