Cowon is definitely an interesting device. For me the lack of keyboard kills it, and the price is higher, especially if you start adding things like the GPS. The Win CE OS has its pluses and minuses, but I consider it overall less appealing than the open Linux platform of the n810.

The advantages are storage, screen size and things like TV out. Disadvantages are that the storage is not solid-state, meaning it's more likely to fail, and of course it's overall bigger and heavier making it less pocket-friendly. The n810 by comparison fits nicely in the hand or pocket.

I think if you're more inclined to a PMP with web browsing capabilities, the Cowon is the device to get. If you're looking for something that is more productivity oriented and focused on things like skype, chat, blogging, email, etc. the n810 is the better choice.