Me? Surely you jest. I NEVER eat humble pie (Rhubarb is my favorite. Offer me Rhubarb pie or crumble with creamy custard and I'll be your friend for life)
Anyway, I digress. Tanous, my friend, thank you for saying absolutely everything that I thought and was going to say about this episode.
http://tanous.livejournal.com/5357.html I'm not too ashamed to say that I was awake all last night mulling it over (the fact that I was also having an asthma attack which was hopefully unrelated did play a part as well!) and it took me a while to work out whether I loved the episode or hated it, I was so torn about the last few minutes and how they made me feel, especially OLD Merlin in the present day. But I went through exactly the same thought process that you did and came up with exactly the same conclusions.
Funnily enough I didn't cry though, not at all, until I foolishly opened a short fic this morning which for some reason I can't fathom had me in floods. I don't handle death well, and I don't handle being the one left behind, having lost most of the people I've loved in my life one after another (happens with age of course :)) I'm with company at the moment so I can't really sit down and watch it again with the new perspective of my comforting conclusions.
One thing I did react to - perhaps a little more positively than you, given your use of the phrase Mary Sue, was the way that Gwen developed. I was bloody annoyed that we didn't get to see any of the three years that turned her into a capable queen, but I made the comment in 5.1 that she actually turned out to be a better and smarter ruler of Camelot than either Uther or Arthur, so I'm not at all surprised that's where she ended up - and after a suitable period of mourning I just bet she and Leon had a marriage of convenience and he ended up being King Leon. I reckon he'd make a good strong king for the country and stop all those other threats from other kingdom, although I would surmise that the fear of Emrys (even unfounded) will keep them at bay for a while.
I choose to believe that Merlin did sneak in and say his goodbyes to Gaius, and possibly even to Gwen, who seemed quite happy to accept him, and I hope that after a period of mourning he did end up travelling the world and seeing and experiencing all those things that being tied to Arthur stopped him from doing. And I hope that he found Aithusa, also in mourning, and ended up healing her and possibly having her with him for a while. I would have LOVED to have seen all that, but do acknowledge that would be a completely different show from the one we've been watching - more of a warlock/dragon road trip which started the heal both of their broken hearts and allowed them to see their long futures before them in a different light. I still feel so so sad that Merlin would be left alone for so long and watch the deaths of everyone he cared about. And I was GUTTED that it turned out to be Gawaine, of all the knights, who died, and never found out about Merlin. But I'm trying to make myself believe that he and Lancelot are now with Arthur somehow, and that they WILL be reborn to be with them when Arthur is released from Avalon.
Although I am on the verge of retracting SOME of the comments I made about the producers being talentless hacks, I still feel that the show they ended up making was not, ultimately, the one I would have loved to watch in its final two years. As you said, once they let the racehorse run, it proved itself so sublime and so capable of outrunning the donkey on the motorbike that I feel deep regret that they didn't allow a much longer period to develop what did not have to be, NEVER had to be, a gay love story if they truly didn't want it to be. All great pairings get 'shipped' whether intentional or not, and it's a crying shame that the show makers recoiled from what was going on in fandom and tried to suppress it, or prove that it couldn't possibly happen. There didn't have to be kisses and making out, for crying out loud, that IS what fan fic is for, in this fandom and in countless others. But they've just proved they COULD write this stuff, so why the sodding hell didn't they write this stuff for the last two years, and give Colin and Bradley the impetus they needed to stretch themselves a little more and maybe, just maybe, decide that they could manage another year after all.
Mostly I'm still sad for the might have beens, but this could have ended much much worse than it did, and for that, I'm thankful for small mercies.