I actually liked Shaw wasn't fawning over Picard and Riker like most Starfleet personnel do. In fact, if you think about it, he has every right to be suspicious of two retired officers making an unscheduled stop then trying to change course. Sure, Picard was a decorated officer and statesman in the Enterprise-D days, but look at the things that happened when Picard and Riker teamed up since then (and some of Picard's solo outings)
1. Lost the Enterprise-D to a 20-year old Klingon Bird of Prey
2. Disobeyed orders and trashed the Enterprise-E, lost probably 3/4 of the crew to the Borg (though Picard did save Earth, so that'd probably score him some brownie points)
3. Disobeyed orders, trashed the Enterprise-E, led an armed rebellion against a Federation admiral
4. Trashed the Enterprise-E
5. Botched up the evacuation of Romulus and Remus, the Jellyfish is lost (most likely trashed)
6. Lost La Sirena
Shaw probably didn't want to oversee ANOTHER lengthy refit of the Titan-A because of whatever shenanigans Picard and Riker had in mind that'd more than likely fuck up his ship