>> At night the, higher power of the MS taillight is just about right, but you'd probably do just as well with some of the new 2 watt flashers.

I would prefer to pay less, but I don't want to have to fiddle with stuff frequently or have failures on the road.
>> Magicshine is the poster child for "you get what you pay for." As long as you don't mind the possibility of paying for it 2 or 3 times, they're great.

1. How bright/safe are MS taillights versus Dinotte?
>> IMO the flash patterns of all the Dinottes are FAR superior to MS, especially at night. The MS is almost as bright as the lowest power Dinotte, but like you say, aiming is an issue. Keep in mind that Dinotte has multiple models that go up from the 140.

2. Has MS come up with a mounting system for the MS taillight or does it still require a DIY solution (this is a frequent problem noted in the reviews)? How does it compare to the way the Dinotte mounts?
>> Unless you want to think outside the box, the MS taillight mount is for the seatpost and nominally angled down (bad), provided you have enough seatpost below your saddlebag. To really take advantage of it, you'll need to add a DIY component or you could use the Dinotte extender bracket for the 140.

3. How are the MS taillights holding up over time? (The comparison is Dinotte, which is legendary for quality and reliability.)
>> Perhaps better stated, "How long did your MS taillight last, before it failed." Mine worked exactly twice. Disassembled and found that the entire circular PC board is prone to rotating if the outer switch ring is stiff to turn. Snap goes the solder joint to the main board, and in my case, it shorted and took the battery out with it.

4. How do these lights work in rain and bad weather (both relative visibility and reliability)?
>> The MS taillight is decidedly NOT waterproof, primarily between the little plastic piece and the metal housing. If water gets between the two, it can work it's way inside the housing. Again, you could seal this up if you wanted.

5. What are the reasons for paying the higher price for the Dinotte and is it worth the premium?
>> IMO the only reason you want to pay big bucks for a taillight is so that you can have enough power to jolt drivers out of whatever else it is that they are doing and alert them to your presence during the DAYtime. To do this with real effectiveness requires some decent power, and heat dissipation ability, and higher capacity batteries, all of which add up to the higher premium. There are those that will tell you (including myself) that an effective daytime beacon is as important as being seen at night. Much of what you're trying to achieve with direct rearward visibility at night can be equally achieved with good reflectors. The high dollar lights tend to be less mass market and more towards high quality and are definitely worth it for daytime visibility.

6. Are there any other pros/cons of these lights I should consider?
>> Pros... they're cheap and when they work, do a reasonably good job. Cons... reliability is VERY hit or miss. You should only buy the MS products from someone like Geoman who at least provides some level of customer service. If you prefer not to go with the Chinese mass market lights, there are a couple of very nice, moderately priced and very high power alternatives out there that fit your run time and single battery requirements.