The few experiences I've had dealing with Dwolla have been positive and fee structure is simple and ridiculously low, especially compared to some other options.  I mostly deal with low-mid sized transactions (typically in the high $XXX range), so 2-4% via BitInstant or a $15 fee for a bank transfer really adds up.  Unfortunately, it seems like Mt. Gox is the only place that actually takes Dwolla; everywhere else that I have seen relies on bank transfers, BitInstant (which is fantastic, BTW), or a slew of alternate e-currency services.  So why no love for Dwolla?  Is it because it is a US-only thing?