Magpul products are very reliable in general. Especially their high capacity AR15 Magazines. That's what I have bought most from this company. I can tell you that their magazines are lighter, easier to load and seem greater quality then the stock mags. The loading magazines are quicker and leads to less fatigue. I believe price is well worth the buy and you get good quality for it that'll last.
Magpul has become the standard for most aftermarket centered builds. They have the consistency for people to keep coming back, and their polymer is very strong and durable. I couldn't imagine magpul not being one of the leaders in the next innovation of the gun parts market.
I think magpul is great, but not all of there stuff is the best for the aftermarket. The magpul bipod is one example. They really just dished out a simple design that kinda works with the angle pivot, however the applicable force to move is either too easy or too difficult. Definitely not something you want to take hunting, where a system like that could actually help you if it worked properly.