I think there are a number of features found only in the Mac edition which Omni should port in some fashion to the iPad if they are serious about making OmniFocus for iPad a true standalone product. Creating perspectives without the use of a Mac is certainly high on the list.
However, the first release of any Omni product is never their final vision for what it should be in the fullness of time. It is a reasonable assumption that many of the OmniFocus for iPad customers were initially OmniFocus for Mac customers. That assumption allows for some flexibility on the decisions about which features must be in 1.0 vs. which features would be nice to have in 1.0. Especially with the built-in perspectives provided, I think OmniFocus for iPad works pretty well on its own, and many of the users who really want to push it are likely to be Mac owners who will want the Mac version as well (which is, after all, a much more powerful and flexible application than the iPad version). As time passes and the installed base grows, however, the set of people left behind by those simplifying assumptions should be getting large enough to merit attention to building perspectives on the iPad, if they are vocal about wanting such a feature. Even those of us who have a Mac would probably make use of it — I know I would, which is why I long ago sent in my request for it to
omnifocus-ipad@omnigroup.com.
Another obvious missing feature is the ability to support project-based perspectives. Ken told me he had some ideas on how to do this, but never got the chance to turn the ideas into code customers could run. If I had to choose between the two, I'm not sure which I would want more, the ability to create/modify perspectives on the iPad, or the ability to have project-mode perspectives on the iPad. It might be safest to request both :-)
Finally, the Mac offers the ability to focus on one or more projects and/or folders, and to switch to context mode showing only the actions from that focused group. This is one of the major advantages the Mac has over the iPad. It can be emulated on the iPad with a perspective, but only if you had the foresight to create one while you were at the Mac. Getting the ability to create perspectives on the iPad gets you a slightly clunky version of this for free (clunky that you have to create a perspective first, but many people will be using the same perspectives over and over (work/personal being an obvious example) so not unacceptably clunky, IMO).