The downside to manufacturer-approved OS updates is that they're often more conservative than some advanced users would prefer. The manufacturer will not release a new version until it has been thoroughly tested and approved. And sometimes they won't advance to a newer version (like going from Ice Cream Sandwich to Jelly Bean) if the tablet's hardware isn't up to the task. That's when many users start to take matters into their own hands.
You may have heard of "jailbreaking" for iPhones and iPads. The same thing is called "rooting" by the Android crowd. This is where users unlock the manufacturer-supplied firmware to install their own updates, customized OSes and apps that factory-supplied operating systems won't accept. There are plenty of tutorials online to walk users through this process.
Before rooting, do some homework to make sure that the tablet and the intended version of Android will play nicely. Processing power and available memory are important issues here. Google provides the minimum requirements for each release, and hopefully so will any modified version of Android. Also, ask around the user forums to see if anyone has already successfully attempted a similar installation with the same type of tablet.
Of course, the downside to rooting is the inherent risk. If done improperly, a tablet can be rendered inoperable, the warranty can voided and the machine can develop security weaknesses [source: TechAdvisory]. And again, before installing a new OS, make sure that your tablet's technical specs are up to par for the new Android platform; having a deficient tablet trying to run a pumped-up operating system could leave the computer running worse than it did before. "Running worse" can range anywhere from excruciatingly slow performance to getting "bricked."
In short, rooting should be left up to advanced users, and even that's no guarantee that everything will go smoothly.