The lack of transaction fees is great. The way that it works with ACH is also good. The api and code examples are all very concise and useful. Review collected by and hosted on G2.com.
I think that the lack of SDKs outside of the 4 or 5 major languages that they provide via the dwolla github account is unfortunate. I would like to see a Golang wrapper eventually. Review collected by and hosted on G2.com.