I believe the issue with "maximum downloads" has since been corrected. Thanks for the heads up on this. Also, the test downloads are free and open to anybody. It should give you a true indication of how your client will behave in a DRM environment regardless of whether you're a Diesel customer as the test ebooks are encrypted.
Regards,
L. Scott Redford
President, Diesel eBooks
http://www.diesel-ebooks.com