You know either one is a winner, so you don't have to regret the purchase.
But personally I think you got the better choice. At least it has the features I find worth wile.
Annotation, highlight, sync books, the best eBook store with usually better prices and selection. The penguin issue was non existent when I purchased my Kindle and should be resolved in the near future. Truly free 3G, I can download books, from any site, and browse on my Kindle.
The one thing I like about the B&N is access to FictionWise, a subsidiary of B&N. FW use to have some great sales but the book selection wasn't so good. However ever since the evil 5 they have not had any great sales and an even poorer book selection.
The batter life I have on my Kindle is about 1 week, due to TTS and 3G. When I turn off 3G and don't use TTS it lasts couple weeks (sorry, I read a lot but don't actually track the hours spent reading, just how often I have to plug in my device)