The good: It bolts right in. It's got decently strong outers. The ring gear is larger than the D30.
The bad: Those outers are the same ones (297-jointed) that XJs have run since 95/96. The ring gear, while larger, is low-pinion and therefore not as strong as the same in high-pinion would be. Therefore, the LP D44 r+p are roughly as strong as the HP D30 r+p used until the 2000 model year XJ. It would be an upgrade over the LP D30 in the '00 and '01 XJ though.
Could-be-good: Locker and 4.10s