Should be able to be used like shadowblade

Casting Spellword is:

Ignius Drakus

Why is this only available for druids?

If you have the dual-wield ability, are you able to make two weapon attacks per turn? (1 with scimitar and 1 with Flame Blade in off hand)

RAW looks like no, as you need to use your action to attack with the flame blade.

Do you think that it can be used in wildshape? I was thinking a giant ape with a flaming blade would be quite a sight to behold.

Quote from vulcanrock >>

Do you think that it can be used in wildshape? I was thinking a giant ape with a flaming blade would be quite a sight to behold.

 RAW:  Yes.

Wild Shape specifies that as long as you cast it beforehand, you can still use actions attached to active spells, while Wild Shaped.

Practically speaking, your specific DM might impose some “common sense” restrictions on forms can actually wield a “blade.”  (Though, a Wolf wield a fire sword in its jaws would be cool).

If you let go of the blade, does that mean you break concentration on the spell and would need to spend a slot to recast it on a bonus action?

No, you can create the blade again as a bonus action if you maintain concentration and the spells duration hasn't expired. 

yes

How do you know if you hit or miss with this? It just says "on a hit...". Do I add anything to a D20 roll for this?

You make a melee spell attack, which is the same as a normal spell attack.

D20+spell casting modifier+proficiency bonus

Got it, thanks.

The very first part of the description: "If you let go of the blade, it disappears, but you can evoke the blade again as a bonus action."

Does this imply that it can be thrown, or you can just sneaky-beaky past some guards/sentries if you need to?

You can't throw it. The moment it's not in your hand, it disappears.

It isn't a bad option for druids, but unless you're running circle of the moon, being in melee often isn't a good thing. I'd take moonbeam for the more reliable damage type, better scaling and range.

XGtE has a similar spell for sorcerers and wizards, dragon's breath; better scaling, has a cone AoE and you can pick the damage type from five choices. Power creep at its finest.

Quote from Rexir2 >>

It isn't a bad option for druids, but unless you're running circle of the moon, being in melee often isn't a good thing. I'd take moonbeam for the more reliable damage type, better scaling and range.

XGtE has a similar spell for sorcerers and wizards, dragon's breath; better scaling, has a cone AoE and you can pick the damage type from five choices. Power creep at its finest.

 There's an even more similar spell for Sorcerers, Warlocks, and Wizards in XGtE - Shadow Blade

Druids have a lot of great options for their concentration.  Flame Blade is not one of them.

If Flame Blade wasn't concentration, I still don't know if it would be worth using.  But it competes with casting spells like Entangle, Faerie Fire, Flaming Sphere, Heat Metal, Hold Person, and Spike Growth among 1st and 2nd level spells. 

I agree with you about Moonbeam. It's better doing an attack roll than doing forcing the enemy to do a Constitution Save, but at least they still take half damage on a successful Constitution Save, which probably cancels out the fact that attack rolls should succeed more often than an enemy fails their Constitution Save.  And you're correct about the damage type and the range being big factors.

How do this spell work with circle of spores? Do I still get the 1d6 poison dmg or is it better do Shillelagh + say booming blade

I would assume you would, since you're attacking with a weapon. It's a conjured weapon, but it's still a weapon.

No essentially you would just make it appear again. That's what I assume based on "evoke"