I haven't had any issues with my cover on my Expilion and mine is 2 or 3 years old; I don't mind it's a little difficult to push close but it has never popped open. My Phillips is difficult to open to but mostly because the little tab to lift it open is too small, but it too is not a beefy plug. I'm not rough with my gear so my stuff may last longer than the normal person. I went to my LBS today and looked at all the lights they had on display, and the covers all were a bit flimsy in nature including the NiteRider, but flimsy to who? Do I wish they were built better? You bet, but this is the world we live in today.
I read Amazon reviews too, and particularly to the complaints. One complaint was some didn't like the mount, really? I find that mount to be fantastic, it was easy to put on the bar, it tightens down securely without movement when riding, it's easy to remove the light from the bracket, and it's built pretty beefy for what it's holding. Another guy somehow pulled the plug out, the only way for that to happen if he pulled on it to hard or from the wrong way, but another guy gave the fix for this even though only a handful of people had an issue with this, the vast majority did not.
Anyway, here is the fix mentioned in Amazon:
The body of the unit is two pieces attached by three philips head screws. The front half is aluminum (contains the light). The black body is plastic. To remove the philips screws you will need a micro screw driver set. Not a cheap set because the srcews are in there pretty tight, you need the micro with the slightly larger handle for leverage. Remove the three screws and the two parts come apart easily. Be careful with the aluminum half as the circuit board is attached to charging port and will come out as one unit. I then reinserted the rubber usb cover and pulled the tab into the body (from the inside of the unit) using hemostats (you can use tweezers).