Had been using mine MS900 since end of February. It get used on an average of 4.5 days a week (sometime I only commute 4 days depending on weather). My morning commute is in the dark regardless of the summer or not. It runs 25 minute a day. So far I have not have any issue yet beside the low battery indicator light comes on somewhat inconsistant when I run the tailight along with the front light. If I try running it for 5 days, it varies anywhere between 1hr 45 min and 2hr 25 min with both set of lights running, but I do not let it run till it totally dead which mean I really dont know how much juice is really left on the pack. So instead of relying on the low indicator light, I just simply charge it once in the middle of the week and once on the weekend.

I can see how the connector is a weak link of the lighthead. I keep mine on the bike at all time minimizing the chance of damaging the wire. As for the battery pack, I have been lucky as it seem the earlier version had issue with those. When my pack do fail, I will most likely not replace it with another MS battery pack. I thinking of making my own using better 18650 such as AW battery and a 2S2P battery holder. I will wrap it in a plasic bag and place that in some hard plastic case and fill it with spray weather foam making it waterproof but yet serviceable (except for the case).

Price is right and well worth it if you have some knowledge of DIY just in case if anything on it fail. I would suggest a better quality light if that will be your only light on the bike and your commute is a must have light for safety reason such as riding in the trail that may not have any lights at all. In my case, I do have a backup light (MGP Pocket Rocket) from Shinining Beam which is just as bright as the MS and serve as a good backup or extra lumination in some area where I need it most.