Okay, some more impressions:
Driving the vehicles around and blasting stuff is fun. They nailed this aspect of the game. In my book, a good open-world game must be fun to pick up for an hour, mess around, accomplish nothing, and still have a good time. Sand Land does that. Most open-world games don't because they lean too heavily on the hamster wheel of checklists and progress bars to give the player the impression of accomplishment.
The game is built around the vehicles. You're expected to use them everywhere, even inside dungeons (which surprised me in a good way). Enemies use them all the time so you'll get a ton of tank versus tank battles. Usually, an open-world game dangles the vehicles over your head but doesn't let you get one for awhile (coughXenoblade Xcough). Sand Land gives you get a tank within 30 minutes, you'll have your garage (for customization) within 90 minutes, and you'll have your second vehicle, the Jump Bot, within 2 or 3 hours. Towns give you a free raptor to ride (hitched up outside the main entrace) so you have a good number of options almost right away. Once you get more vehicles, you can switch between them on the fly inside and outside of combat. So, you can ride in with your speedy bike, switch to the Jump Bot for some close-range stomping + grenades, then switch again to the tank for some mid-range armor piercing shots. Your ammo is unlimited, and while one gun is reloading you can switch to another to stay on the offensive. Every part of combat and map-exploration flows really well. It isn't "innovative", sure, but you'd be hard pressed to find something that drags the experience down if vehicle combat is what you're looking for.
The load times are almost instant, whether I'm loading up my save, switching between panels in the menu, or using fast-travel. Even teleporting from one end of the map to the other only takes 1 second... the screen briefly goes black and then immediately returns to the gameplay. This doesn't make the game good, but it's definitely worth praising the game for it. You collect resources from things that you smash (barrels, trees, crystals embedded in the wall, etc), and most open-world games would force you to get off your vehicle to stoop over and pick up resources or to swing your pick axe. In Sand Land, you can mine ores and even open up chests from within your vehicle without having to get out.... hardly an industry-shattering concept, but in the moment-to-moment gameplay, it's nice not having to constantly get in and out of your tank to pick up some cactus fragments or open up a treasure chest. Resource gathering isn't a huge focus anyway, but making it more convenient to grab stuff was a smart move.
It's hard to put my finger on the tone of the game. It's not "silly", but it doesn't take itself too seriously either. It shares a lot of elements with grittier open-world games like Mad Max 2015 and Nier but also feels like Jak & Daxter 3. The music is different than I expected but fits right in with that PS2/PS3 RPG vibe.
My kids all love it. Despite the T rating (for language), it's very kid friendly. My two sons are about as far into the story as I am, and my youngest is content to drive around in the tank or Jump Bot shooting whatever she sees. They love the humor and they're excited to unlock more customizations for their tank.
Most importantly, the game is exactly as it seems, an open-world vehicle combat game. So if that's what you want, that's what you're getting.