IanR - could you send an email to our support to look at why you get no file back? I'm sure they will solve it quickly, they might need some info from you.
As far as on device viewer, you're both right
. The devices are faster now, but the issue remains J2ME. It is a limited version of desktop Java and is missing a lot of components necessary for PDF processing. It is also substantially slower and has memory limitations. This is why everybody goes for server conversion.