I've bought quite a bit from them... Even subscribed to some of the magazine subscriptions. I think they are a bit on the pricey side for products and shipping, but customer service has always been really good.
Understanding basic Japanese Grammar is there listed with $ 18 plus shipping.
ichigoichie
Just to let you know that I bought UBJG from J box a few weeks ago and I had no problems. It took a few more days then usual due to it being out of stock at the time, but no complaints. That was the cheapest place for that book.
I ordered from Canada. I can't remember how long it took, but I'm guessing 1-2 weeks.
US, here. Some things only took a few days, some took a couple weeks. I'm assuming that some things were shipped directly from Japan (magazines) while others (t-shirts) were shipped from the US. Probably depends on how new/popular an item is.