Just got an R8 for the bar and R2 for helmet. These are my observations.
OMFG it’s (R8) bright! But wait, that’s not full power! ZOMG, it’s mega bright! Still not full power?! KABOOM! Now we’re talking!
To be honest, the first of the 3 ‘proper’ modes is bright enough for the speed I ride at, so the battery will last forever, but 3000 measured lumens is, as they said in the singletrack review, addictive, and you only get an hours fix from the (massive, heavy) battery, which doesn’t mount very securely with the supplied strap. Helpfully I have an old district one that’s much more solid, so I use that. You could get around that by putting the battery in a pocket an use the supplied extension cable. My only gripe about the mount is that it is 31.8, and my new bike will have 35mm bars, so I’ll have to get another one. It’s way better than the rubber oring round the bar type affairs and I like that it mounts the light centrally.
The R2 is a great complement to it as a helmet light, though the mount isn’t great and difficult to get really tight and secure, but that might just be my helmet making things difficult, as it has small vents so not my room for the Velcro. I’ve also used it as a bar light, and it’s fine, but the R8 has spoiled me. I got the bigger 4 cell battery too so battery life is brilliant on that.
Obviously they are both beautifully made, and look great too.
The reason I went for them over exposure is I like the idea of having a few spare batteries ready during races, or to have them charging on rotation. I also like having the weight of the battery in a back pocket, or within the frame, rather than on the bars or on a helmet. Horses for courses though I guess.
Definitely go for a helmet light too, even if you go for the R8, it’s nice to see what’s directly in front of you at slower speeds, and to look round corners before you get to them