I just saw this thread, or would have jumped in sooner.
I've owned four Spirit XZ's, now down to three. (JerryJ has my XZ-2DB.) All are quality, good sounding, good playing, comfortable basses. There's nothing to not like. Put quality strings on them, like Steinberger rounds, and they rock out.
They are pretty easily modded if you want something different, sound wise. The Audere passive harnesses work well with the EMG Select pickups. I've done a variety of mods; do a search on Spirit and Michaelvee and you'll find a number of threads, including a megathread.
The main thing that has changed since I started playing Spirits back in 2001 is that they are no longer available wholesale through MusicYo. You have to buy them for full retail now, and on top of that, the wonderful XZs are no longer available, just the XTs.
The XTs are solid as a rock, being one piece maple. But they have balance issues on a strap. Take a look at the Synapse basses, which come with a strap hook. To play an XT comfortably standing up, you have to come up with something similar to the hook.
The XZ basses can sometimes be found on eBay and sell for a premium these days. Even so, they are worth the price.
In the seven years I've played XZs, I kept hoping they'd catch on among Talkbass bassists. They never really did, so I, and a few other mavericks carry on nonetheless.