Responsive websites are starting to increase in popularity, and forum software will eventually start adapting to it. These sites scale automatically depending on the device being used by looking at the device's resolution. There are plenty of frameworks out there that give developers the base CSS code to create these sites quickly (twitter bootstrap is a good one that is increasingly popular).
There are a few great reasons to do a responsive website instead of a mobile version, a desktop version and an app. One, you have one site to maintain and modify. Two, there is no need for users to install or purchase anything (this is a very big deterrant for the majority of users. People want free ****, so keep it free if you can). Responsive websites done right also look lke full versions on tables in the horizontal view.
Tapatalk is OK, but again, its 3 bucks and I have 3 devices I view the site on outside of my desktop which means 9 bucks for something that Id rather just view in a browser? GMAFB.
Taco should seriously consider looking at other forum software too as vBulletin is old, dated and none of the upgrades I have seen over the years have fixed the core problems of vBulletin. Its slow because all of the html and css is stored in a freaking database which causes heavy load on the DB servers and requires way more resources than it should. Even if they used a bloated templating engine like smarty, it would be ten times faster than it is now.
I frequent a college board that uses XenForo and I really like the forum. Its sleek, has a lot of very cool features, is fast. Not sure what Isaac's budget is but he should look into it. Get the eff away from vBulletin.