I have buy from gwing 3 time, wide range of selection. Delivery time is good as well, the longest time I waited is not more then a week anyway, so it is acceptable for me.
Overall, a good option if you looking for some rare items.

Pricing wise, gwing stand in the middle I guess, compare to forum, etc.

Oh , I never tried their pre-order, but they are usually quite updated to latest product, so it is a nice site.