(this gif isn't the entire scene but that's the gist)
It's a small sequence, but one that I really like. Getting to see some glimpses of the nitty gritty of the automail creation process is, for one, neat, but I think is also significant because:
First, while Ed having automail is established from the very start, but at first, at least to me, it felt more like just the way for Ed to have 4 functioning limbs, and this was the episode was the introduction to it as an actual real part of this world, if that makes sense. That automail is something that has people specializing in it, that there's a lot of work and skill that goes toward making and maintaining it. Seeing some of that process really went a long way to set that impression. And second, for Winry specifically, again, seeing some of the process really helped get across how much time and effort she's actually putting in to get this arm made for Ed. That's a simpler concept to articulate, so I didn't write as much about it, but I feel this is actually the part that's more significant.
It may ultimately be a few short glimpses of the process, but I feel that's a very effective way to establish it as a complex, involved and time consuming process we happen to catch brief snippets of (like Ed who just sees whatever part Winry is currently on when he periodically bugs her). For how brief the scene is, if it wasn't in I feel the effects I mentioned would be much, much lesser. If after Winry goes to work, next time we see her it's pretty much just to install the arm and do the finishing touches. Maybe what I'm saying doesn't make sense to someone else, or they think I'm overanalyzing a minor scene, but I remember feeling a lot of this even on my first watch.
Also, Ed and Winry interactions are obviously appealing to me, but I do actually like the scene mainly for the reasons I wrote here, though that is a nice bonus.
What made the scene extra noteworthy to me, and also appreciate it more, is that it actually wasn't in the manga. It's something Brotherhood thought to add. And it's something I really liked, it stood out to me even on my blind first watch, and it really felt like it was missing not having it in the manga.