This does not look like a good weapon. Don't judge a sword by its.... Scabbard?
characters don't like it because it is only so-much better then a Machete or .45 Automatic and takes away a slot or you intend to get a big gun later anyway. But then. Whats the harm in an additional big weapon that doesn't count against deck slots? Consistency and efficiency is the name of the game and this big-ass sword is a great way to add a little weapon-finding consistency to your deck mid-campaign.
Non- might have dramatically different opinions. The massive +3 to hit can turn a mediocre fighter into a warmachine. "Skids" O'Toole, Finn Edwards, Diana Stanley, fighting at +6. Rita Young or Silas Marsh with their inability to gain superior in-faction weapons that will last them an entire scenario will be looking at Timeworn Brand as a main weapon, if you happen to find one of these on the way that'd be outright awesome, if only for consistency's sake!
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So, with the "who wants it" covered, lets look at what it does.
Its an infinite use +3 +1 damage weapon, at this moment that's the largest + infinite weapon in the game. So damn yes that's got the attention of the fighty characters.
And then there's the ability to literally teleport around the map, to wherever more opponents might hide. This ability wont always be useful. In solo you can expect a couple maps per campaign where you're chasing a Doom carrier or some scenario specific agent, the saved actions as you shift around the map, batman-style, are terrific, but definitely not always useful. This ability ramps up very quickly in usefulness when you're fighting the threats that come into play in a 3 or 4-player game though, also note that the Khopesh lets you bypass the Aloof keyword.
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So yes, I don't think this is ever a bad weapon to put into a deck that's interested in killing enemies and not hugely dependent on hand slots. Even if it's not as good as a Lightning Gun, just keep in mind the importance of consistency.