LED flashlight is sure no longer a niche technology. Now, you can buy this kind of flashlight at almost any store, and many of the good ones are not even that expensive.
However, while LED flashlight nowadays has better quality than regular flashlight with common bulb, you must pay attention to the quality like you do when choosing other products.
What must be looked at when you are choosing an LED flashlight? Here are some:
Basically, the lumen amounts determine the brightness level of your LED flashlight. The more lumens an LED flashlight has, the brighter it becomes, and of course the more expensive it will be. Therefore, choose wisely.
If you are buying one for indoor use, 10 lumens are enough. If your area often experiences blackouts or you are picking some for your 72-Hour survival kit, you might want to add another flashlight with larger amount of lumens (say, 100 to 300).
If you are often do outdoor activities such as hiking, perhaps you need flashlight with more than 300 lumens.
Most LED flashlights have on-off button on their rear parts, but you will also find some that have more traditional on-off switches.
Basically, it is all about convenience; which one is more convenient for your hand, than choose it. However, if you need a flashlight for activities that require tactical ability, such as a job as police officer, the ones with rear on-off button will be your advantage (common example is Maglite that is carried by many police officers in the US).
Each battery type has different characteristic that determine your LED flashlight performance. Regular batteries such as AA and AAA are easy to get and last quite long, but you must buy the new ones every time. Rechargeable batteries are more expensive and last in shorter period than regular batteries, but you can save battery money in the future. If you only use batteries at home, you may want to buy rechargeable batteries. If you spend much time outdoor, buy regular LED flashlight and stock regular batteries.