Yeah, I think Jack was nice. I've been vocal in this thread before about how I really don't like NTR stuff in NTS, and Jack was perfect in that regard. He was always super respectful, didn't overstep his boundaries, had a good relationship with the MC. He served as a great partner for their sex play, even helped take the phone pics during the BJ, and let the couple focus on just enjoying their kink. And because it was on an island vacation, they're likely never gonna see him again, so it feels like a nice no-strings-attached affair. (Amusingly, someone earlier in the thread had this theory that Jack's wealthy connections could mean he's related to the mafia, and as a result he could show up in the future. I dunno that I care about seeing him back, but I thought that was a funny idea.) I feel like I would've preferred less escalation during the vacation, and having the first sex sometime after they get back home, but that's not a Jack problem per se. Overall, for a first time partner, I think he worked well.
Geist is great so far. I think the spat he had with the couple made him very likable. He's also super upstanding, but the more manly physique and personality make him more interesting and exciting as a partner. You could get some great scenes out of him.