It isn't overly crazy. One of the beauties of it is that the Homunculus servant can use it. This allow the Artificer to scale a bit with the other classes by using their bonus action to have their HC cast a one action utility spell. It is most fun to solve problems with outside of combat. Sneaking a party through a crowded room one at a time with a serious of invisibility spells and how to move the item back to the next party member.

That's incorrect.  The magic item Spell Storing Ring requires attunement, but the item created by the Artificer ability does not.  That also means that, yes, you can put Invisibility on it and then pass it around to make the whole party Invisible, though that would require the concentration of everyone in the party.

The one thing I consider genuinely cheese about the Spell Storing Item is giving it to a familiar to cast.  That's technically RAW, but I'm not a fan.

The familiar trick is limited by the ability to use hands. The artificer’s homunculus servant is of a choosing of the player, so it may have hands — though be sure to check with your DM.

Quote from Shaylic >>

I mean there aren't many spells that could be abused by having a good con save. Artificers get Flash of Genius which will help with saves and they can create an amulet of health at 14 to get a 19 Con. What are you afraid they won't stop concentrating on spider climb, heat metal, or enlarge/reduce. I think the strongest use of the SSI is to store cure wounds for 10d8 healing +10 x int mod over the course of a minute.

Flash of Genius

Starting at 7th level, you gain the ability to come up with solutions under pressure. When you or another creature you can see within 30 feet of you makes an ability check or a saving throw, you can use your reaction to add your Intelligence modifier to the roll.

You can use this feature a number of times equal to your Intelligence modifier (minimum of once). You regain all expended uses when you finish a long rest.

^^ This is right on. The SSI is absolutely not overpowered.  You are limited by the artificer spell list, which really doesn't have any 1st or 2nd level spells that blow a campaign off course in Third Tier, or even turn the tides on an encounter.  Has anyone ever thought Web was OP?

I am currently playing a 13th level artillerist in a campaign with a 13th level battle smith.  The SSI isn't overpowered. It is nice, but by the time you get it, it is almost an afterthought.  Our wizard is casting Force Cage at this level, for crying out loud.  Our fighter is attacking 6 times with action surge. Our sorcerer-warlock is spamming Eldritch Blast at ridiculous levels. 

Between the two of us, we have loaded it with Scorching Ray (kind of a waste... Fire Bolt does about the same damage), Web (fun- we handed it to the Steel Defender),  Blur (a bit of a waste of ten slots), and now that the Druid left the campaign, Cure Wounds.  Cure Wounds is probably the most bang for the buck from this item.

Shatter is a fine spell, but when you consider an artillerist with the Enhanced Arcane Focus giving a Fire Bolt +12 to hit with 3d10 damage, plus the 1d8 from an arcane firearm, the 3d8 with a CON save for shatter is a worse option, every time.

It is not OP.  I would call it "nice" at best.

I find myself struggling to use it more than twice in a game day until I settled on Cure Wounds.

Oh, I should note, neither of us have used the Tiny Servant gambit.  The tactic in that article about making multiple tiny servants that hand the SSI to each other, and firing off all the charges in one round would not be allowed at our table.

 Believe me, I was pretty excited about the SSI until my character got one. It is underwhelming. 

Tiny servants with SSI can reach pretty high levels of ridiculousness as they can use all ten charges at once for some pretty juicy burst damage at level 11. Tiny servants can also be used with other magic items. These combos are only limited by your creativity. I have an idea of a artillerist with both eldritch canons, tiny servants with wands of magic missiles and SSI with scorching ray or shatter so they become mobile artillery. This was all discussed in a good thread The TSAR: Tiny Servant Actuated Robot, a Revolution in Artificer Combat. (giantitp.com). It is a bit outdated though it should give you some ideas. 

Tiny servants is a good spell but but you have to use multiple spell slots to get enough for ten. Animate objects on the other hand just uses just one fifth level spell and gets you ten small or tiny creatures that follow your instructions. I have a combo with catapult and acid vials strapped together that does some serious damage. 

True but with TS you can give them standing orders since artificers have other uses for their bonus action. 

Thisnmakes up for all the features and spell sots the artificer doesnt have, except half the spells they cast have to be the same spell. It's really the double concentration that the artificer gets, but only for 1st and 2nd level spells, and when most campaigns are already wrapping up.

As an artificer looking at the SSI, one thing that caught me was that my humonculus servant CAN'T use it very well, since it cannot talk to cast any spell with a verbal component.

You aren't strictly casting the spell here.  So no somatic nor verbal. It is an Action to produce the effect.   If you were casting the spell whole sale it would say take an action to cast the spell. Not produce the spells effect.

So, anything that can take an action, can use it just fine it seems.

This also has some implications on the Haste spell. As it seems to be an object use action (as it does not specify any other action,  and you are using an item)

While holding the object, a creature can take an action to produce the spell’s effect from it, using your spellcasting ability modifier. If the spell requires concentration, the creature must concentrate. The spell stays in the object until it’s been used a number of times equal to twice your Intelligence modifier (minimum of twice) or until you use this feature again to store a spell in an object.

Thank you for the correciton.

Looking at it, I also realize that the Tentacle Rod I took off that drow priestess is another great item to equip to my little buddy.  Since you use an action to direct the rod to attack, not to attack yourself.