All right, after putting about 20 hours into Warframe (inside like 6 days, mad!), I've got Things to say.
First of all, the core gameplay is fantastic. Seriously, the guns feel great, meele's even better and when you're doing content for which you're not underlevelled, Digital Extremes somehow managed to create a looter shooter which doesn't need spongy enemies to function - so you're murderizing dudes left, right and center while zooming around and using abilities that can cause anything raging from instant death of a bunch of guys all the way to a small extinction event. (Unless under-levelled) you never feel like you're shooting enemies with peas and slapping them around with a rubber duck - weapons have weight to them and they're balanced enough to allow you to just pick your poison and stick with it. There's also functional stealth and parkour system, both of which are an optimal way of getting through some levels - optimal, but not required.
And while we're at picking your poison, while I may just not have progressed far enough to see any of it, there doesn't seem to be such a thing as a 'superior' weapon that you'd find in, say, Borderlands. All weapons seem to be sidegrades with varied behavior, but none seem to necessarily be more powerful than another one - and if that does turn out to be the case, I'm going to love this system. See, there's mods that can be levelled up and made more powerful. These mods are what makes weapons more powerful and they're transferable between weapons of the same class - so you can totally use a different weapon and have it as powerful as the one you were using previously simply by transferring those (that's not entirely true, there's also a gear levelling system, but let's forget that for now)
Yeah, loving this design, loving the gameplay. I'm even ejoying exploring the individual levels a whole lot, albeit procedural generation can sometimes create bits which make absolutely no sense - still, exploration is fun and when you find something rare, you feel rather good about it.
Now, for the Switch port. Let me just say that the little console has no damn right of running something this pretty, but... It does! The performance was a bit dodgy once I started, but it turned out there's actually quite a lot of graphics settings to fine-tune it to a fidelity you find acceptable while getting table performance (so I basically turned off all the graphical bells and whistles and while I barely notice the difference in how the game looks, I sure do see the difference in how it performs - the thing's running silky smooth.) The game's absolutely enjoyable in both handheld and docked modes - what I find a bit more irritating is that, even in solo mode, it just refuses to handle the console going to sleep and then waking up - when you do so, the game restarts, abandoning whatever mission you were doing at the time.
Anyway, if Warframe is something you find remotely interesting but go "Eww! Free to play!", give it a shot. It's really good - and that's coming from a guy who did so in the past, bounced off and decided he'll never play it again. ... But did. And damn.