I ran it yesterday too, and have been reflecting on the experience. Long post warning...
It wasn't my first marathon, it was my 8th, so I had something to compare it with.
I've heard a couple of people say it was really busy on the course, but I didn't feel that at all - I always felt I had plenty of space to run in, and was never impeded by people deciding to walk (in that there was enough space for people to move over to do so). Maybe it was more crowded in earlier waves (I was in wave 7).
I was a bit surprised not to strike up conversations along the way too, but that may have been my own fault, as I ended up running a fair bit faster than planned, so kind of got myself into a bit of a focused place, to try and maintain it until the end. Perhaps if I'd been thinking less about my pace etc, I might have been more chatty.
I'm totally with you about the course! It is DULL! I really felt for all the foreign runners (of which there were loads) who must be expecting to 'see London', but you just see the Cutty Sark, Tower Bridge (which was very 'meh', I felt) and then Big Ben etc at the end (Canary Wharf does NOT count as a landmark, IMO). However, the crowd support totally made up for the dullness for me. I've run marathons on beautiful courses with very little support and I know which I'd choose every time.
And yes, the finish is a bit weird. You just kind of cross the line, and that's it. I was expecting to feel quite emotional, but I just felt quite pleased with myself in a reasonably understated kind of way. I felt more emotional when I checked my phone a few minutes later and saw so many messages from people who had tracked me, and was very touched by how much support I'd had, without even knowing it.
BUT - here's the thing that really gets me (rant alert...) Every single marathon is the same length. They're all 26.2 miles long, and they all need the same training. And most of them are on much more challenging courses than London (which has no uphill to speak of). But London gets all the attention, all the kudos and all the plaudits. People are just not interested in other marathons, despite the fact that completion is just as much of an achievement. It really grids my gears. It's like people think that London is some kind of super-human feat, more so than any other marathon. In reality, London was the easiest marathon I've run - partly because I was really well prepared, but mainly because of the amazing crowd support. They really do get you round. It was on my bucket list because I just wanted to know whether what everyone said about it being an amazing race is true (and I think, on balance, that it is), but I wish every marathon got the same level of appreciation, because you have to work that bit harder for all the others.
Having said all that, I'm so glad to have had the experience. I'll remember it forever, and it was a very special day, like no other race I've been in. I have entered the ballot for next year, and I'd love to do it again. But I do wish it wasn't up there on a pedestal and seen as the most epic achievement above all others.