What are your thoughts on this universe and the series? I thought it was an enjoyable ongoing. Thought I wish Elektra's past (why did she become a nanny?) and the reason behind Angel (Fallen) becoming evil were explored more. Besides those two, most if not all of the subplots were resolved at the end of the series. The ending feels a bit rushed, however, probably a case of dwindling sales necessitating the story to be cut short.
Characters from this universe rarely showed up outside of the Mutant X series. It is probably partially because most of them got killed by the Goblin Queen. The other reason is likely because the story did not prove to be very popular. Barely anyone talks about it nowadays and in its heyday, it still only lasted 32 issues and 3 annuals, so more like a moderate success.
Also, Mutant X Havok appeared in Exiles, but he was nonsensically turned evil. In the Mutant X series, he was indeed said to be a colder person than the 616 Havok, but it was not to the point where he was a psychopath. Mutant X Havok was the leader of a superhero team, nonetheless.
Could this have been a testing ground for the Ultimate Universe? Mutant X came out two years before Ultimate Spider-Man. It was an alternate interpretation of the regular continuity just like 1610. Albeit it was more of a wacky AU story than a modernization attempt like Ultimate, but still.