Yes, particularly flights to/from JFK from the west coast. I've flown it twice between SFO and JFK. The "true" window seats are pretty private, since you're separated from the aisle by a side table; but not as private as one of the B6 suites (e.g., row 2), and the finishes on the product are a little cheap looking (ugly blue upholstery). Nonetheless, I've been impressed by the seat and the soft product; until a year ago, I hadn't flown Delta for at least 6-7 years, since it's not big in SF. It's pretty nice when you can get it for ~$550 each way, since that's roughly what I'd end up paying to buy MC and a T-24 upgrade on VX. But I think B6 Mint Suite is a clear step up.

Isn't AA 321T the one vessel on which AA offers 3-class service; and wasn't the OP's question about First, not Biz, on the 321T?