1. There is no way to have multiple taxes configured, even though they have a multiple tax option. You can't have taxes based on shipping address for different cities. You can globally assign one tax rate to a state and not charge other states, but if you have to charge different tax rates within a state based on the shippers city, it is not possible.
2. Non-taxable items. They claim to be able to do this, which it can be done, but for some reason they have tied "non-taxable items" to the item weight. So if you don't want to charge tax on something then you don't put an item weight in the configuration. But then if the customer only orders that item that is non-taxable and has no weight, then the shipping module doesn't bring up the shipping options (like their UPS Shipping Module). Why would you tie "non-taxable items" to a shipping weight.
3. Customizable emails are virtually non-existent - unless you are a php guru. There are no templates for emails that are easy to manipulate. The initial email that a consumer receives on the order looks great. Subsequent emails are a simple text email that looks very elementary and as of the date of this review...the forums, the developers have provided no answers.
4. Before you use this extension, go register and get into the forums and look at the questions and see how many responses there are from actual developers vs. forum members.
There are other little things to that are annoyances, but are fairly easy to overcome. However, the items I have described are big, not just for me but for a lot of users. The tax thing is huge.
If you need a simple, out of the box (so to speak) solution with no complications for tax implications, no need for custom emails to your buyers, and just want to sell all items with one flat tax, then I would agree, this product is pretty easy to use.
I have lots of good things to say also. I am just being candid about the issues.