There are always areas of improvement Steve. Not sure we can learn much from Saints though. They play the game completely different to us and it's a rare sporting team that can do everything better than everyone else. Saints have they're own limitations which seem to be getting exposed now they have a few injuries.
Interestingly this very topic was discussed early in the season and the Saints' posters on here didn't agree that we could cope with injuries much better than they could. They argued that injuries wouldn't show as much because we'd be replacing ordinary players with other ordinary players. Well the likes of Smith were anything but ordinary on Saturday!
So, to answer your question, what can we learn from playing them last weekend? Well, firstly that we can beat them. Secondly, to repeat it next time we have to do what we do better than they do what they do. And finally that we can't afford to gift possession and position in the way we did at the start of the 2nd half.
I expect Saints will come back at us. I wouldn't want anything less. Keep improving as we are though and it'll be an interesting season