Ages Pretty Well On Average
I recently picked up the 20th Anniversary edition of this seminal issue for a few reasons. First of all, I thought it was great timing what with Uncanny X-Men Vol 2 #1 coming out as a great point of comparison. Second, as someone who has always really been into the X-Men, I thought it would be neat - especially since I've been so steeped in it recently - collecting trade paperbacks and whatnot. Third, these are the X-Men I knew from the 1994 cartoon.
Just like Uncanny Vol 2 #1, this issue spends a lot of time re-introducing new readers to the team. As DC knows (the whole point of the new 52) you're going to pick up some new readers whenever you have an issue #1. That said, the art (in a general sense) of comic book storytelling has evolved a bit since then, so there are a few things that make the book feel a little dated. The dialog is very comic book-y. "Oh, I've been captured, I better escape" and stuff like that where their internal monologue is less about realism and more about talking to the reader. Also, the use of thought bubbles which have all but been eliminated in today's comics.
Interestingly, the technology and style of dress aren't TOO 1990s.
From someone 20 years in the future it's interesting to see how cyclical comics are - Magneto went from terrorist to X-Men helper to being a loner in this issue to being a terrorist again to being master of genosha to being a loner to being friends with the X-Men (now) to being a terrorist again (possibly with next week's Magneto mini). Wolverine and Scott are almost at Schism-level fighting.
I read it mostly as a curiosity, but it has piqued my interest in this time period in X-Men comics. I'm still working on getting caught up in the trades from Morrison's run onwards, but I think once I'm caught up I might go back and get the classics.
Bonus: check out the bonus pages to see who used to be a villian and is now allied with the X-Men. Lots of fun there!