1. Extremely talented Bluetooth engineers. Chris and Martijn were second to none.
2. Very good diagnostics tools built in house. When a user complained of connectivity issues, we could take a snapshot of the state of their Bluetooth stack. This gave us amazing insights into what was going wrong- more often than not we found that iOS and Android were doing something unexpected (we had lots of workarounds for their bugs). FWIW a few of us went on to start a company to build more of those hardware debug tools: Memfault (W19).
If Memfault ever want to end the standalone external tool supplier gambit and return to being in-house expertise, sounds like they could be very useful there. Not because Garmin's BT is so terrible (it has improved a lot but still far from perfect), but because Garmin seems to be the smallest living company that still builds their own stack down to the lower levels instead of hitching a ride on something like an Android fork.
The proprietary RTOS that runs on the watches is a super cool embedded system dating back to the earliest days of the company. It grew across all the product lines - watches, nav units, aviation equipment, marine chartplotters/sensors, etc. I remember once stumbling on some code written in the very early days by an engineer who went on to be the CEO while I was there.
It was a fun system to work on, and had an impressive amount of code sharing at the OS-level across platforms as tiny as Cortex M0 systems up to large multi-core ARM SoCs from TI and other vendors.
I just looked them up on eBay, looks like you can get another for <$50.
I wonder if there's going to be a Pebble maintenance scene in 20 years, I wouldn't be too surprised if there was.
I'd estimate I still get about 5 days of battery (depending on how much solitaire I play, or how long I use the speedometer app).
Every other smartwatch I've tried (a couple fitbits, fossils, etc) has been absurdly flaky. It's common for all of them to just not react to notifications for a couple hours. Or they'll connect to some wifi but not others (why wifi anyway!?? it's insane! it's SO much more complicated!). Or their apps have utterly monstrous installation and/or permissions setups (looking at you in particular, Fitbit) and any connection they use breaks randomly every few days.
If I could just get another, I'd stick with a pebble time for probably a decade. It did almost everything right.