The HTC Sensation is my second Android phone (my first was a MyTouch 3G), so I've been running Android for a few years now. For a long time (up until yesterday, actually), I used the stock operating system. I didn't want to worry about rooting or installing a custom ROM on my device. It seemed like it would be a hassle, and I had heard enough horror stories about custom builds that it made me wonder if all of the basic functionality on my phone would even continue to work. I had heard woeful tales of non-functioning GPS and read angry forum posts about sub-par graphics. I knew there were all sorts of nice things I could do with my phone once I rooted, but I didn't really want to spend the time that it would take to get it working. And of course I wanted to avoid bricking it.
Then, about a month ago, my phone was laying on my desk and suddenly the screen lit up, announcing a call. It was my brother, but when I answered, I received a cryptic error message telling me that android.phone.something had crashed. This continued to happen every time he called. I was smart enough to try turning it off and on again, but to no avail. I was stuck with a phone that was a little bit spastic in delivering its core functionality.
I figured that a factory reset of the phone would probably fix the problem, but that would require re-downloading and reconfiguring all of my apps. HTC had announced that they were planning on providing an over-the-air (OTA) upgrade of the stock OS to the newest version of Android (version 4.0, which is called Ice Cream Sandwich and abbreviated ICS) by the end of the month. I figured I could wait and upgrade, and hopefully that would take care of all of my problems. Then I learned that the update was going to be delayed indefinitely, so I decided that the time was right to dive in and see what I could do about my phone.
The entire process took me most of the day on Sunday, but in the end I had a nicely functioning phone. It actually felt like it was brand new; the phone seemed to be faster and smoother than before I started, and I have yet to experience any problems. I'm not going to delve into all of the details here, but xda-developers is a great resource for anyone interested in learning more about the process for a particular device.