i thoroughly dislike Garmin, but my igpsport 630s is a joke of a device. they never fixed ghost watts, and i did a sprint session yesterday, which completely invalidates the session. Every single time you go riding "hard", you get corrupted data. They don't give a F, they deflect, at this point it's safe to say they'll never fix it.
The navigation is way worse than garmin (which is bad already). You sound like you're driving the clown car when you're following a route with the igp630s. the thing beeps constantly the moment you're not riding a straight line. a slightly curving road, with no intersection and no possible doubt as to where to go, beeps CONSTANTLY saying go left, go right, it's absolutely retarded. And they also seem completely uninterested in fixing it.
The gear number w Ltwoo does sync on the device, but battery level doesnt.
On the plus side, my computer mount decided to die on a mean downhill this week, the computer flew off the bike at 60kmh, and it still works. The screen broke further, but it was broken already.
And credit where credit is due: the hardware is fast. the app sync is fast. Getting the data imported back into garmin is a bit of an art form. the export, depending on the format you use, is corrupted, something they also dont seem interested in fixing. if you do .tcx, you get basic data exported well. if you do .gpx, you get more data (including temp), but half of it is completely wrong so it's unusable.
It could be a great device, it just isnt. i paid 155 eur for it, i would have returned it but i couldnt. the ghost watts stuff is just unacceptable on so many levels. for casual riding, it's ok. for anybody serious, it isnt. Imagine doing some kind of "ultra" event and the thing stupidly beeping on you for 15 hours, hell no. And it's not like you'd want to deactivate the beeping altogether, because i m not riding to stare at my screen, and the off course / re-routing thing is also worse than garmin, so if you happen to go off-course, good luck making sense of what's the route, what was the route, which way is the route, and so on.
last: i tried to see if there's an open source stack / some way to hack the software, looks like it's closed source and not an option. if the software could be open sourced, it could be a wonderful device.