Pros:
Easy to use and great User Interface
Process 100s of Images with few clicks and within Minutes
Inbuilt Watermark Placement Options
Feature to Add EXIF Info
Upload Watermarked Images to Picasa/Flickr Easily

Cons:
The license is tied to the OS, if anything bad occurs, and you don't have time to deactivate the software (how to do this? Ask the support! ), the key doesn't work anymore.
You'll have to open a ticket on the Mass Watermark support, for one time your license will be activated. If any bad happens to your disk or you decide to upgrade the OS and forget to deactivate the program, you will receive the answer that I've received below from the support:
"Sorry for any inconvenience caused.But the discounted license only allows limited activation.
Before you reinstall your OS there is an option to deactivate Mass Watermark. When I checked your last ticket I have found that we mentioned this to you. (my note: you don't have the right to forget this...)
I don't mean that you are trying to violate the license terms but as per our policy there is nothing we can do.
You are free to use any software of your choice."
This is the consideration granted to the customer !!!!! Stay away!!!