Great pistols; probably one of the better "secret values" in defensive .380 caliber guns.
As mentioned, they use a gas-operated ("blowback") system, which can produce a little more perceived recoil than an identically-balanced and weighted gun with a recoil-operated system.
The Thunder also uses the once-normal DA/SA trigger operation, so the hammer, cocked after chambering the first round, can be lowered, and the gun fired from that state. Each subsequent shot would be fired from the lighter, hammer-cocked, state.
The finish on these tends to be fairly Spartan and lackluster, usually a matte-black painted finish on black models. The frame is aluminum, and the slide, steel. The gun balances well in most hands (a higher-capacity "Thunder Plus" model that fills the hand even more is available) and I find it easily-controlled, and surprisingly reliable with all kinds of old and new ammo I've run through mine. Pretty accurate as well. I'm glad to own mine.
In a nutshell, I'll give it thumbs up for: excellent reliability, good balance, crisp trigger (especially in SA-mode), three-dot sights, generous beavertail, easy takedown, and value.
I'd give it a thumbs down for: lackluster finish (though it does keep cost down), budget-feeling plastic grip stocks, and (to some people) excessive size for the caliber.