it is a pretty sound system! it achieves perfectly what it goes for: a fast paced medieval fantasy military adventure. it has room for a lot of strategy, but also for a lot of luck. it's the best board game I've ever played (ok, I'm not that into board games) and I love how it is structured, making it a miniature game without you having to organize the best army.
I've never played BoW. I understand there are great differences between the two games, but, as I don't have a feel of how BoW rules work for BoW, I couldn't compare them with BL. what I can risk to say is that BoW rules doesn't seem to be a very good idea in a BL game. and that is not to say a thing about how BoW being released as "a BL game" in a time where we weren't seeing any future for BL made all of us BL fans at least a little jumpy about BoW (go and ask Frag abou being closer to "explosive" ;] ).
I do love Martin's universe and I would like to play BoW very much. but I've invested a lot in BL so far, and, as I'm from Brazil, buying games through Internet, paying mail taxes and risking outrageous importantion taxes is not a thing that makes you so eager to start a new game investment. I'm hoping to complete every BL box (waiting to see the repurposed ones) and then I can start thinking about other things.