Last year I wrote this extensive review of the first Apple Watch, where I talked about hardware and software. It was one of the my favorite reviews I've ever written, and I stand by almost everything I wrote then. Here's how that review ended:

However, if you are still on the fence, don’t feel like you need to rush out and order one today. Almost all of my current problems with the Apple Watch will be fixed by software and hardware releases down the road. We expect to see an SDK for apps to run natively on the Watch either this summer or fall, and we’ll almost certainly see a new version of the hardware with faster internals within the next year or two. Apple is betting big on this thing, so expect them to work tirelessly to make you want one.

It's been 16 months since I wrote that review and I'm pleased that Apple has indeed addressed many of my concerns raised in that original critique. watchOS 3 has made the software a lot better (read my full watchOS 3 review here), and they have revved the hardware with the Series 1 and 2 lines. For a brief breakdown of what specs are different between the 2015 Apple Watch and the Series 1 and Series 2 models, I made this chart to make it as clear as possible:

The big concern for most owners of the original Apple Watch was performance, and both the new models have an upgraded CPU that bring more power to the device. Beyond that, the Series 1 is exactly the same as the original Apple Watch in every other way. It's supposed to be 0.5mm wider and taller than the original model, but I cant tell a bit of difference on my wrist. The Series 2 adds better water resistance and GPS, while the Series 1 still requires your iPhone for GPS tracking and is equally as water resistant as the original.

Please note that since I have only spent 2 full days with the new Apple Watch, that's not enough time to judge it's battery life well. I will say that so far it seems to be right in line with the old model, but I'll follow up in a week or so with how it performs.

It's all about speed

The only real significant change from the original Apple Watch to the Apple Watch Series 1 is the dual core S1P processor on board this new model. Apple advertises 50% more performance in this chip than the S1 that shipped in the original Watch. That's a little hard to benchmark, but I believe the claim based in my time with the new hardware.

watchOS 3 did a lot to make the Apple Watch feel faster already, and this 50% faster CPU makes everything just fly. The best way I think I can describe it is that the original Apple Watch always felt like it was being pushed to its limits at all times, even when it was going fast. The new Series 1 Apple Watch is going a little faster, but feels like it's doing everything with ease.

I think this feeling stems mostly from the fluidity of animations that trump everything I experienced on the first Apple Watch. Animations are as smooth as you would expect from Apple, a company that is always looking to achieve a constant 60 frames-per-second for all interactions. It's still not perfect, and some actions show the slightest bit of stuttering, but everything from scrolling through notifications, to launching apps, to navigating the app honeycomb, all move fluidly.

In addition to a generally smoother experience, there are 3 things I have found are immediately improved by the added speed.

The most impactful change is that the raise-to-wake feature seems to be faster than before. The Apple Watch famously (an frustratingly) does not have an always-on display, so you must either turn your wrist or tap the screen to see anything. I've never had any real trouble with this functionality, but I have definitely noticed the screen turns itself on faster than it did before. It's not much faster, and some people may not notice it, but it's a nice, if tiny change.

The next big improvement is in how fast apps you do not have saved to your Dock or watch face complications load. watchOS 3 made your docked/complication apps launch instantly, but everything else was still terribly slow. With the new hardware, those other apps don't launch instantly, but they sure do launch faster than before. Instead of waiting 5-10 seconds for those apps to load, it's more like 2-3 seconds. It's not a game-changer, but it does make me more likely to use those less-used apps more often.

Finally, the last improvement I noticed was that workout apps, specifically RunKeeper and Strava, update themselves much faster mid-workout. RunKeeper especially would take a few seconds to refresh its data when I raised my wrist in the middle of a run, but with the new hardware it's updating nearly instantaneously. Again, it's a little thing, but it's one of those things that you will appreciate a ton if you do a couple workouts per week.

Everything else

This is a weird review to write because everything else is the same from the old Apple Watch. And I don't mean that in the cynical way some reviewers say the "s" year iPhones look the same and therefore are the same. No, I mean every other spec is exactly the same as the previous model. It looks and feels the same, the same watch bands work just as well, and it runs the same version of watchOS software. Unlike the Series 2 models, this does not have additional hardware features or enhancements beyond the speed bump.

Conclusion

If you didn't buy an Apple Watch before because you heard the Apple Watch was slow, then I think this is a very good place to jump in on the platform. Combined with watchOS 3, the new CPU inside this watch makes this a wearable that I don't think most people would even consider calling "slow" anymore. However, if it wasn't the slowness, but the core functionality of the Apple Watch that kept you from buying the old model, this isn't going to change your mind. For those people, the Series 2 watches may be of more interest, as they add GPS and better water resistance to the mix.

The real question is whether current Apple Watch owners should upgrade. That answer is a little more fuzzy. On the one hand, the Series 1 Apple Watch is a solid performance upgrade over the original model, and I'm personally happy with my decision to upgrade. But on the other hand, you just got a big speed bump in watchOS 3, so you might be happy for another year with what you have. I paid $399 for my first Apple Watch and was able to sell it online for $230. At $299 for the Series 1, I'm only $70 out of pocket for this new one. That was totally worth it for me, but if I hadn't sold the old one for a good price I probably would not have gotten this one at all.