The Galaxy Watch runs Samsung's in-house Tizen operating system, and man, it has come along way since the old days. Samsung says there are thousands of apps and watch faces available for the Galaxy Watch, and the company does a respectable job highlighting the really good stuff in its Galaxy Apps store.
While the number of Watch-friendly Tizen apps has grown pretty dramatically over the years, I'd warn you not to confuse quantity with quality. The biggest problem with Tizen right now is the same one it's always had: There's some useful stuff available, but many major app developers and services haven't thrown their support behind the platform. Sure, heavyweights like Spotify and Uber are on board, but you might run into trouble if you want specific apps on your wrist.
And then there's Bixby, the Samsung-made virtual assistant that has, uh, largely failed to impress. It's here on the Galaxy Watch to field all of your voice commands, and if nothing else, the basics are well tended to. Bixby was always quick to notice when I was calling for it, and it had little trouble sending messages and tracking exercise when asked. (That's no small feat considering I shattered a tooth partway through the review process.)
While Google Assistant and Siri largely retain their features and personalities on their respective wearables, Bixby on the Galaxy Watch just doesn't. Bixby's main draw on smartphones was that it allowed you to make fairly nuanced requests and tap into third-party software, neither of which work here. You can ask it general-knowledge questions, but it flounders more often than not. And sometimes Bixby suggests things to ask it, like "search Bermuda Triangle" -- it's just too bad that the assistant had no idea what to do with that command aside from flashing an error on-screen. Bixby might be improving on phones, but on watches? Forget about it. Google Assistant and Siri are distinctly better.
Samsung's virtual assistant might be pretty lousy, but hey, at least the Galaxy Watch is every bit the fitness tracker that the Gear Sport was. Actually, scratch that: It's even better. The Galaxy Watch can track 39 different exercises, from traditional fare like running and bench presses to more-niche options. (Here's looking at you, burpee test!) My one regret in writing this review is that my schlubby body couldn't handle all 39 exercises, but the ones I did try worked quite well. It took a toll on the Watch's battery life, but my few GPS-tracked runs seemed nice and accurate. And despite the fact that circuit training nearly killed me, the number of calories it claimed I burned were in line with results from wearables like the Fitbit Versa.