I will answer from my experience.
1. I have used both and Minicam is much better functionally. They both recoed video but minicam has taken it to the next level in terms or being able to customize it for your hardware.
2. GPS overlay allows you to add the data from your GPS receiver on the screen. Alt, speed, direction, time, and date and such. The nice thing is it is written by the author of Xport and so you do not need to tie up a virtual com port to get data to it. It just works. The overlay data can be set to automatically change color based on the image behind it so it is always visible. Very nice feature!
3. Yes it works in windows 7. I have run it in XP, Vista, and Win7 32-bit.
4. I am not sure about when features were added I am describing the features that are present in the current build. Bottom line is it works great. I use it with a USB camera with a built in mic to record out my front window and the resulting files are nice.

