Arriving in Switzerland from Italy.... any customs to go through?

Italy and Switzerland are both in the Schengen zone, so no.

Thank you. I thought not, but good to have it confirmed.

Customs is never the issue, it is immigration/passport control when you move outside of the Schengen zone or into.

Sorry to correct the previous posters, but technically there is customs between Italy and Switzerland, because Switzerland is not in the EU. But, this consists of one or two Swiss and Italian customs officers watching people entering or leaving Tirano RhB station. They certainly do not stop train passengers unless you are very suspicious looking, and there is no need to allow any extra time for customs.
There is no passport control, because both Switzerland and Italy are in the Schengen Area.

There are no immigration controls, but there could be a custom control. I do not know in Tirano, where the controls should be in the RhB station, but in Chiasso (another Swiss/Italian border point) there are occasional controls, usually geared to intercepting Italians importing/exporting undeclared cash from/to Switzerland, or Swiss citizens shopping in Italy and importing too much things without paying duties.