I run a fairly high volume low margin web business selling on 5 channels. After using various shipping software and ShipWorks being the last one, I have finally found the one that fits all my needs.
ShipStation is total web based, so I can use it anywhere and their interface is very simple and efficient. Due to the volume, it is all about automation and simplicity for me. Shipstation was very user friendly to pick up and I was literally off and running within one hour. After signing up the free Endicia and Express1 account, I did some configuration on the shipping labels and start downloading orders. It was pretty easy and had no issues. On Amazon orders, it download all the weights given by Amazon and even had pictures of the SKU in each order. After adjusting the weights (it will remember weight by SKU), I process my first batch. It verify all the address and split out any errors such as missing weight, no zip code, address too long, etc. After fixing errors, you can print out the shipping labels in 4x6 or whatever format you would like. It also allow you to print out the packing slips and a pick list for that batch for easy processing. The pick list even have pictures and optional location info if you setup that part. I have found the pick list to be a life saver and it also works as sort of an error checker for me.
Regarding extra features, I will go over couple of them that I use:
1) Shipstation has built in filters for international orders and by different channel. I had to do some reading to create filters for priority and multiple SKU orders. You can combine filters into automation rules.
2) There are bunch of reports you can print out and run on the fly or download them into PDF. I use some of the reports and is quite nice.
3) There is a loading dock feature where you can drag multiple orders for processing. It is actually quite ingenious and i found lot of uses for it.
All and all, I am very happy with Shipstation. I figure it has save me at least 1 to 2 hours a day in shipping and decrease my shipping errors dramatically. It is truly amazing how much thought was put into each feature and how every effort was made to make this software easy to use and user friendly.