A couple of caveats to my opinion:
1. I've not used Roambi and can't speak to strengths / weaknesses.
2. I don't speak officially for Tableau nor do I have any inside knowledge of their road map.
Having said that, I would be willing to bet that Tableau will move much faster toward addressing the weaknesses you listed than any other tool is likely to move toward being as easy and intuitive to use. Tableau is very committed to the ubiquity of their product and they've made no secret of the fact that they see mobile as key to that. And I think Tableau for Mac is included in the "Top Pain Points" list, so I wouldn't be surprised if that is addressed soon too.
Tableau did say at the Customer Conference that they will be releasing Mac and Linux versions this year. Other than that I can't add anything to what Joshua said.
Thanks for the feedback. I agree that Tableau is very likely to address these gaps soon, given their track record of rapidly introducing seismic updates.
Regarding the Mac and Linux versions, I assume that pertains to Reader? Do you know if there are any plans (or that the capability exists) to introduce an offline version for tablets?
you could export the dashboards as .png or .pdf if i remember right, so a workaround could be to design a very simple web page with just reports name, and getting report's details trough your web server and feeding tabcmd application with necessary command line flags.
Doing this, users could get very fast the reports by email. It's a poor man option but without huge resources (cash, staff, time) one could address this business issues.