TELLES0808: Arcade isn't really my concern and doesn't really seem to be a point of sale, so I'm unaware of any 3rd-party plugin issues that may arise when using it. I'm making games so that, hopefully, I can sell them. So, is posting to the Arcade a big deal? For me, absolutely not, and it may be better to be concerned with finishing a game than where it could, potentially, maybe, possibly, end up. Considering the literally hundreds of other places you could place your HTML5 game, not being able to put it in one specific place, so unless it's highly-trafficked - I'd put money on, say, Kongregate getting more hits - shouldn't be a big deal.
Madfactory: Dude, yes.
You have to do this in every tilemap editor I've ever used, and what I've used goes back to the early 1980's, so I think it's safe to assume that's a lot of them.
I have no hand-typed list of properties. That's a) if you feel the need to do it, what spreadsheets are for and b) you don't really need to do it since you can just click on a tile to see its properties.
What do you mean, no visual representation? I see them just fine. Are you talking about in C2? In which case, that's not really relevant, since it's your job to build the tilemap after import through the importer, and pretty much how full OO game development works, whether in C2 or Flash, Unity, C+, etc. I've had huge Flash AS3 projects go through from start to finish without placing a single object on-screen manually for reasons other than testing it looks/works okay.
Tiles can be comped together into a single image using Canvas. If I'm able to figure out how to reduce 20,000+ tilemaps down to 800 or so (for collision/active objects), I have no doubt you can as well, not to mention the same multiple-object issue would exist with a built-in editor. I haven't been using C2 all that long - and other than the usual beta software quirks, I have yet to hit a wall in terms of making it do what I need it to do.
Just because C2 has a layout editor doesn't mean it has to be used.
As for importing TMX files at runtime, you answered your own question there. I expect there are other ways to make it happen as well, since you can pass a variable value as a filename to the AJAX object.
As for Tiled's workflow: Want to see a bad workflow? Look up Cosmigo Pro Motion, the go-to for pixel art/animation. I'll just say this: be glad Tiled is as easy to use as it is, and that it supports highly advanced 2D map-making features completely unavailable elsewhere, all for the cost of FREE. There's a reason (lots of them actually) game studios working on 2D tile-based game often default to using Tiled if they don't plan on a user-facing in-game editor.
I've had zero issues with the workflow of the TMX Importer. I do have a good bit of development experience though, so I haven't had any workflow issues and found it only took a few hours to get it doing exactly what I wanted it to do, mostly because I had to learn the associated events.
I think a lot of this discussion just sounds like people aren't aware that more often than not, no single program is the be-all end-all solution to every request. I think you'd have nightmares or at the very least break out in hives about some of the programs that you have to use in AAA game development if you expect C2 to do everything for you.