I can think of a scenario where being immortal would be worthwhile. If you could be assured of being among similar beings (whether you become like the others or they are always like you), AND you had the ability to forget what you know when you want to. The most fun is when you are a blank slate learning all sorts of new things. Once you've been there and done EVERYTHING (many, many times), I'm sure being immortal would really suck. Even more so, can you even imagine what it would be like if you OUTLIVED THE PLANET??? Eventually, the sun would expand and die taking the planet with it. Now you're just hanging out in dark space... Hell indeed!