I've been skiing at the Blue Mountain for four years or so, and keep coming back having tried most other mountains in the NYC area.
Its greatest strength is night skiing. It's really a day-trip mountain, and for night skiing you don't have to get up at 5 on a weekend morning as you would for all other decent mountains around NYC. All trails are lit, and the quality of lighting couldn't be better. We usually ski on Sunday nights (we work on Saturdays), and it's dirt cheap: $19 for 4-10pm; and crowds are thin to nonexistent. We leave the mountain at 10 and are back home in Queens around midnight.
Snowmaking and grooming is another major strength. Most of the time, the snow is very good compared to other resorts in the East. Naturally, when the day is warm you can expect some ice at night, but usually it's no big deal. I believe their grooming is about as good as Belleayre, and way better than Hunter (which was mostly raw ice whenever I skied there).
The staff are very helpful and friendly. You can check-in your skis for free, quite convenient. The lower lodge, on the face of it, is only average but feels quite cozy.
On the flip side, they have few trails. When you look hard you realize that the Blue basically has two each of double diamond, black, blue, and green trails (plus sundry short trails and passes, and several very good school areas). It's great for beginners to strong-intermediates, but expert skiers will probably quickly get bored of the two double-diamonds, even though they're steep and utilize all of the vertical drop (at 1000', the highest in the Poconos). The park is supposed to be good, but I cannot judge since I don't use it.
On the balance, night skiing, decent vertical drop, good snow, accessibility from NYC, and coziness of the place makes it our favorite local mountain.