Good, While a Missed Opportunity
To preface, i haven't played any wargames myself, and as of time of writing haven't gotten the chance to test the rules out myself.
The product gives you what it tells you; It gives you a handful of rules for making & managing multiple units (Extra's & Wild Cards) on the battlefield at once. It also gives you sample units (9 Extra units, 8 Wild Card units). And that's it. For Pay What You Want, that's not bad.
There are a few things i miss, though. Generally the rules provided are basically what i believe one could conceivably come up with on your own in an afternoon. Which for $3 I think is good value, but i wish there was more. Firstly, it only very briefly touches on combat Scenarios and provides nothing in terms of generating scenarios itself. So you'll have to find generators somewhere else or come up with your own. Secondly, It mentions that Wild Cards can only have Hindrances related to combat. And of all the Hindrances in SWADE Core, depending on how you interpret "related to combat", is at most half of the existing ones. Yet it provides no new Hindrances that could relate to combat to make up for this. Lastly, some of the sample Wild Cards units have the Battle skill, which is used in Mass Combat. But since this isn't the same Mass Combat as is in SWADE, i wish it would explain why those units have it. I'd like expansion on what the Battle skill can be used for more specifically in these kinds of "mass combats".
I might be expecting too much from this little supplement, though. As a simple introductory piece, i think it gives you what you need, and i look forward to trying it out. I enjoy Savage Worlds combat, and hope this helps make it more interesting.
TL;DR: All in all, I like it. I only wish it had more content (and then probably a higher price-tag, which i would be OK to pay if it had what I'm missing). There's missed opportunity here, i feel. I hope the writers work on and expand this more in the future.