The gameplay loop is pretty faithful to the original as far as I remember (it's been a few years). I did notice a few differences compared to the Untold version of 1 which threw me for a loop (they added a "hint" system in Etrian Odyssey Untold to give you an audio cue that there is a hidden passageway nearby, which is absent in this version and the original DS version).
The map controls are a bit awkward and unintuitive for me, at least so far. I imagine they're more intuitive on PC with a mouse, but it's not that big a deal.
As far as how it's aged: the only thing which really makes it feel a bit aged to me is the rather high random encounter rate. If you're used to more recent dungeon crawlers like this, they have fewer, more meaningful encounters on average; the EO series has a lot of simpler encounters that are there to drain your resources, and to make it a bit of a gamble about whether you can avoid the FOE who's chasing you. It's not bad, but it's something to consider.
Ooh, didn't have this on my radar, I'll have to watch for it.