The integration works really well. No major drawbacks at all. However, for each Size and Color variation you have to assign the same model all over again. The best solution so far has prepared ScalablePress. There you may bulk assignment for the different sizes and colors.
As mentioned in the previous reviews the major disadvantages are: prices and prolonged turn around period. I would personally recommend you to check other POD Shopify apps this includes Print Aura and Pressera.
Really slow delivery. It took almost 4 weeks to get the shipment in. My customers started complaining :/
Rock And Lock Apparel
I've been using Printful for a few months after weighing my options. I previously operated a store on another platform and had a terrible experience with the print quality & shipping speed. Printful does a far better job on the print quality front, but just as bad in shipping. So bad, that I've had to discount a customer's order due to the speed of fulfillment. I realize that there's most likely a huge number of orders every week, but fulfilling a customer's order shouldn't take 2 weeks. I'm rating 3 stars, as I also understand that Printful saves me loads of money on overhead, since I treat this is a low-to-no-investment business.
This may be a great app and service but it is not easy to get started and to get Smartify and Printful working together. The video says it is easy, but it has not worked for me and i have been trying it for hours.