I’m using Cateye TL-LD1100 (the one with 2 rows of leds that can be switched independently). It’s bright, has good side visibility and is surprisingly good on batteries. I was also using a 2×0,5W rear light as a backup. Not stupidly bright, but pretty good. With those lights on still not all drivers pass me with safe distance.
This fed me up a bit and I now have swapped the 2×0,5W light for a Magicshine rear light. Runs off the standard battery from Magicshine light, has a 3W led + 9 smaller LEDs and is very bright. It’s pointed slightly downwards so is not blinding drivers but leaves a noticeable red light trail behind the bike. It’s hard not to notice it even at day time. This combo might be a bit over the top now, but does the job especially now when it’s getting dark pretty quick.
+1 for the RSP, had that one on another bike, bright enough and very good visibility.