I dunno what its rep is. Maybe I won't get any argument. 
I've always felt this was my favorite episode of TNG's first season, but until today I haven't really stopped to think about why. But I think I've cracked it.
It's because it presents us with a very TOS-like situation, but told in a very TNG-like way.
In some ways it's very progressive, sort of showing the tenements of the character based strengths that would come to define The Next Generation when it finally found its feet in seasons two and three. It could be the first TNG in this regard, perfectly blending those character moments into the action.
On the other hand, the script seems to work to counter criticisms at the time that TNG wasn't as 'action based' as TOS. So you've got a situation which deliberately places the landing party in danger, with the opportunity for lots of TOS-style phaser fights, and a heightened sense of danger for the Enterprise in orbit as well. I do remember many pundits, including MAD Magazine in their parody of the series, making a lot of TNG not seeming as action packed as TOS, so 'The Arsenal of Freedom' comes as something of a reminder that this isn't necessarily true, and that TNG can handle action shoot 'em ups with the best of them.
I also like the message behind the episode, and the relevence it has. Like the best of TOS, it tells a story in allegory, but doesn't necessarily beat you over the head with its message. It perfectly manages to satirize both the weapons trade in particular and capitalism more generally.
The Next Generation had a pretty ropey start all things being told, but I honestly felt that by 'The Arsenal of Freedom' they were really beginning to cook with gas. It's by far my favorite episode of the first season.

I've always felt this was my favorite episode of TNG's first season, but until today I haven't really stopped to think about why. But I think I've cracked it.
It's because it presents us with a very TOS-like situation, but told in a very TNG-like way.
In some ways it's very progressive, sort of showing the tenements of the character based strengths that would come to define The Next Generation when it finally found its feet in seasons two and three. It could be the first TNG in this regard, perfectly blending those character moments into the action.
On the other hand, the script seems to work to counter criticisms at the time that TNG wasn't as 'action based' as TOS. So you've got a situation which deliberately places the landing party in danger, with the opportunity for lots of TOS-style phaser fights, and a heightened sense of danger for the Enterprise in orbit as well. I do remember many pundits, including MAD Magazine in their parody of the series, making a lot of TNG not seeming as action packed as TOS, so 'The Arsenal of Freedom' comes as something of a reminder that this isn't necessarily true, and that TNG can handle action shoot 'em ups with the best of them.
I also like the message behind the episode, and the relevence it has. Like the best of TOS, it tells a story in allegory, but doesn't necessarily beat you over the head with its message. It perfectly manages to satirize both the weapons trade in particular and capitalism more generally.
The Next Generation had a pretty ropey start all things being told, but I honestly felt that by 'The Arsenal of Freedom' they were really beginning to cook with gas. It's by far my favorite episode of the first season.
