Here is a link to a photo of the Kingfisher A321 Business Class that I clicked on my recent GOI-BOM flight.
http://tinyurl.com/59mtvs
As can be seen from the picture, there is extra legroom available at the exit row seat.
Rest assured, they do not use this door for boarding. Boarding is always done using the front door. (and sometimes front + rear door)
One thing to note though - If you choose seats C&D, you would have an F/A sitting there facing you. Don't know if you would be bothered by this or not, but thought I'd mention this.
- Vivek