Hell yes I take immortality, even with the negative aspects as I think you could work around them.
1. Yes you could possibly be out evolved, however you would have knowledge and experience on your side. I magine any new sentient beings would make the same mistakes as humans have and I sure these new creatures are smart enough to know having someone who has lived through all this before could offer invaluable advice. Or if that fails remind them that I have one advantage over them, I can't become extinct they can and there is a likely chance that my body will still carry extinct human viruses and bacteria that these creatures aren't immune to. MUHAHAHAHA!
2. I suppose I could try and hide my immortality eg, changing my hair colour to grey and such as if I where ageing. Though that would only last so long as eventually people are going to start wondering why there is a supposedly 90 year man walking round with no wrinkles or health problems. Though if people do come after me again they need to remember I'm immortal, bullets and knives are like neetle stings to me, so if there coming for to use me for evil purposes they better have alot of expendable henchmen. Though if they come wanting to worship as a god then my ego might just allow it
3. That is a possibility, though I still could keep records and photographs which would certainly jog the memory banks. Also the human brain can hold serveral lifetimes of memories if wasn't for old age and death getting in the way. Staying forever at the peak of my bodies condition I imagine would help slow the loss of memory down quite a bit.
4. Time would possibly fly by quicker and quicker, but I imagine your perspective of how time passes would adapt. Also given that appear time passes quicker you get older maybe because it becomes clear that you will eventually get old and die, which by then you realise that there isn't enough time to do everything you want to do. If the prospect of old age and death is then taken away, in my opinion it might be possilbe that the reverse happens and time appears to go slower like when your a kid as your not worrying getting older and just living in the moment.
5. Getting trapped would be a problem that unfortunately you could nothing about unless you are rescued or soil erotion eventually frees you. Being stuck on this planet after it becomes uninhabitable could be more avoidalbe though, as the sun won't die for hundreds of millions of years, who knows what science will have uncovered in that time. I could possibly leave the planet and travel to a new planet, or even time travel could be possible by then and I could just go back to very beginning of the Earth and live through it all again. At least that way I have a way to go back and see loved ones that have died off, or if I eventually get bored, imitate Wowbagger and insult everyone in existence.