This spell can be odd.

One thing to note about this (especially if you're fighting mages or spell-casting creatures) is that it prevents you from being counter-spelled, regardless of the level of Counterspell used. Seriously useful if your DM (or your players if you are the DM) has a habit of doing that.

So do conventional weapons go through?   What about magical weapons?

you can walk right into it its not a wall of force so yes you can shoot or melee attack things inside it

It seems to serve as a zone of anti-magic. So effectively any magical properties would be cancelled inside of the globe.

Not really.  It just blocks spells.  Antimagic is a whole other thing

Not at all. You can still cast spells from inside. It only prevents creatures outside of the globe from hurting you with spells.

My mistake then....But it would cancel EXISTING spell effects in the area it is cast....correct?

Doesn't appear to.  It just blocks incoming magic

It's like putting on a bulletproof vest.  Putting one on doesn't remove the bullets you were already hit with.

Not necessarily since counterspell works by keeping a caster from fully casting a spell.  Globe of Invulnerability only works once fully cast so it would keep any level of Dispel Magic from working though.  Honestly if I were a DM I'd rule Counterspell would potentially work

Quote from Henchmen1980 >>

Not necessarily since counterspell works by keeping a caster from fully casting a spell.  Globe of Invulnerability only works once fully cast so it would keep any level of Dispel Magic from working though.  Honestly if I were a DM I'd rule Counterspell would potentially work

I think Charred meant other spells cast from within an existing globe, is difficult to counter.

Counter spell should work when you are casting this globe. The spell hasn’t taken effect yet when counter spell would be used. The barrier hasn’t been placed yet; you are going through the motions of casting, speaking the words required, and using the component necessary to cast also if counter spell is successful the bead would shatter like the spell says at the end of the spell. 

You can counter the globe but after casting it your other spells can't be countered. I think Dispel Magic works on the Globe. Sage Advice covered this spell pretty extensively if you have questions about it.

This is one of the spells an MM Archmage takes. It's not that impressive ..... nor are some of the other spell choices. A few counterspells and absorb elements might free up this higher level spell slot. 

Quote from Iron_Theurge >>

This is one of the spells an MM Archmage takes. It's not that impressive ..... nor are some of the other spell choices. A few counterspells and absorb elements might free up this higher level spell slot. 

 Absorb elements is from the Elemental Evil Player’s Companion, so it is not an option. In what way is it underwhelming?

One other thing to note is that the globe only blocks spells cast OUTSIDE the sphere. If a creature first moves inside the globe and then casts a spell, such as shocking grasp or booming blade, according to RAW that spell would not be blocked by the globe.

Quote from SomewhatCharred >>

One thing to note about this (especially if you're fighting mages or spell-casting creatures) is that it prevents you from being counter-spelled, regardless of the level of Counterspell used. Seriously useful if your DM (or your players if you are the DM) has a habit of doing that.

 unless you counterspell this spell obviously

Quote from Charmandenator >>

You can counter the globe but after casting it your other spells can't be countered. I think Dispel Magic works on the Globe. Sage Advice covered this spell pretty extensively if you have questions about it.

 Raw, the spell only protects creatures and objects IN the dome. Since the dome isn't inside of itself, any dispelling or cancelling should work on the globe.

Looks like it to me.  Looking at the spell description for Dispel Magic - "Choose one creature, object, or magical effect within range. "  The Globe is a magical effect so it could be targeted by Dispel Magic.  The problem is, the caster who's casting Dispel Magic would also have to see this 'faintly shimmering barrier' and know that it is indeed a magical effect.  That problem could certainly be solved based on the level/cr of the character as the higher the level, the more experienced the character, or through a couple of ability checks, I suppose.  Question:  If using ability checks to spot the globe, that would - at least in my thought process - take the character's focus as they would have to specifically be looking for it.  How many rounds should such searching take given the time frame involved?  (6 sec/round)