Your iPad, NOOK, or Kindle Fire do have some restrictions. The Kindle Fire runs a modified version of Android without Google Play. Not all NOOKs offer Google Play support either. iOS devices have their own issues. By jailbreaking and rooting your tablets, you can install more apps and get more out of them. Here are 3 tools that let you jailbreak your iPad, NOOK, or Kindle Fire device:
Evasion: a pretty nice jailbreak tool for iOS devices that have not been updated to iOS 6.1.3. It works for iPhone, iPad, and iPod Touch and brings Cydia to them in a flash. We will have to wait to see whether these guys will release a jailbreak for iOS 7.
N2A for Android: want to turn your Kindle Fire into an Android 4.2 tablet? The N2Aos service has you covered. You can also restore your Kindle back to its original software with Restore2Stock.
N2A Cards: these cards turn your NOOKs into Android tablets. They work for older NOOK devices too.
Should you jailbreak or root your tablet? There are going to be risks involved. Many people have done it without any major issue though. The above tools make jailbreaking your tablet a lot easier.