Always a fan of created my own integrations through RESTlets, but obviously its a bit more difficult to maintain and change.
Celigo would be my recomendation for an iPass solution. They have built in NetSuite connectors that make it really easy to use. As well as some pre-configured data loaders.
Easy to set up, easy to configure, easy to maintain with low/no coding required
Downsides are cost. its not terribly expensive, but it is an added cost as opposed to writing your own integrations. Also there is a bit of a learning curve getting started with it, and if you need anything done outside of the pre-built connectors you'll have to spend a little time playing with it to get it to work.
They have an excellent certification program that is easy to knock out in a day if you dedicate full time to it. They set you up well to get started using their system. And the certification is free