This 'rare' item seems to me to be decidedly LESS useful than the 'uncommon' Bag of Holding.

agreed

It's meant to be more useful as far as finding the object you intend to find out of it, where as the BoH was meant to be more cluttered to sort through. In practice, they didn't implement it well enough and most DMs are more than willing to ignore this for both cool factor and speed of the game.

Probably why it's rarer; less people making these since they're less useful 

people say this isn't useful, but imagine combining this with the bag of holding, portable hole, and efficient quiver, so you could carry huge amounts of stuff and it would weigh nothing

Handy Haversacks also have their uses in games where encumbrance is a thing.  That seems stupid to say, but remember - the haversack weighs 5 pounds when loaded, while a Bag of Holding weighs fifteen.  Remembering that anything you want access to quickly needs to be on you and not in the bag, saving those ten pounds could be important in some niche cases.  Rolled a character with 4 Strength recently; even without variant encumbrance I was counting pounds.  Would much rather have a Haversack on said character than a bag of holding.

That's admittedly a niche case though.  In most cases, the Bag of Holding will do the job.

I used to be a traveling merchant, until I got shot in the backpack with an arrow.

"Placing the haversack inside an extradimensional space created by a bag of holding, portable hole, or similar item instantly destroys both items and opens a gate to the Astral Plane. The gate originates where the one item was placed inside the other. Any creature within 10 feet of the gate is sucked through it and deposited in a random location on the Astral Plane. The gate then closes. The gate is one-way only and can't be reopened."

You can pick this up with Mage Hand, whereas a Bag of Holding is too heavy for a Mage Hand to lift... so I guess you can use it for BBEG banishment.

I think one of the best things to use with this item is the spell instant summons. You could basically prepare a bug-out bag somewhere if you’re in a place that requires your belongings to be removed from you. Just have the sapphire set in a piece of jewelry or, if you want to get real inventive with it, see if you can get a false tooth containing it so even if you’re stripped down its highly unlikely that it’ll get ripped out of you.

my gm uses variant encumbrance so this is a lot better than a bag o' holding especially for my str 2 character 

This carries 120lbs of gear using a total 120 cubic feet of space. Surely this should be common or uncommon at best? Maybe if it was re-balanced to not reduce the weight but to allow strong characters to carry more than the basic backpack allows and then reducing the rarity it would see more use? 

Bruh if u put roadkill in there you could ask for edible meat and it would take the edible stuff and separate them

I'm pretty sure "edible meat" is not a "specific item". At best, it is a part of a specific item. At worst, it's a specific concept. 

But most likely cheaper than a bag of holding, and travellers without the coin to get a bag of holding would still be able to get a pretty good bag.

Can you place a sharp object inside the Haversack?  Or will that cut it?

I mean ask your dm If i was them i would ask you to roll a dex check and below 10- it cuts it

That's.... that's not how those items work but i wish it was

Dimensions of the large pouch question. 

Unlike the bag of holding which specifies that the pouch is 4ft deep and 64 cuft total, implying the the interior dimensions are about a 4ft cube; the description on the haversack just includes the total of 8 cuft. Would that imply that area adjusts for the object put in as long as it doesnt exceed parameters?

EX: My group wants to deal with a large size sentient weapon(9ft greatsword) by putting it into a haversack and then dealing with the creature that it is dominating. Other than doing some math to see if it would  exceed the 80lbs weight limit, i am inclined to let it happen.

Thoughts?

Maybe switching it to uncommon and not rare, and then the BoH to rare?