This is one of the most amusing questions I've ever seen, mostly because it's akin to asking if Tiffany's is a reputable jeweler, or perhaps if Rolex is a good watchmaker.
You can't know that until you get into photography, of course, or one of their other areas of expertise, like video. I remember not knowing anything about B&H, and it's why I didn't get my D300 from them (not a good call).
B&H is the standard all other photography retailers are judged by. Adorama is great too, but B&H is the king. I don't see that changing anytime soon.
B&H is the largest privately owned photo store in America, and they're consistently cheaper than Adorama. Only bring relevant details into the thread.
Adorama has excellent prices as well, and in fact two lenses and two cameras of mine came from Adorama. They were used and in great condition. My F5 was listed as being in E condition for $335. A terrific deal, and it's understandable that they raised the price a bit.