Re: Not Yet -- what about Surface?
It depends whether you're using the Surface by itself or (if it's a Pro) with the docking station.
The Surface tablets can handle laptop duties in a pinch, but they're too small for heavy keyboard work. At the same time, they also offer so-so pure tablet experiences.
The iPad isn't very good at laptop duties (though that doesn't stop people from trying with third-party keyboards), but it offers a superb pure tablet experience. A desktop, meanwhile, is way more productive than a Surface for heavy productivity. Bigger screen, bigger keyboard-- that stuff matters, at least to me.
So if you're talking about the Surface by itself, I think an iPad + desktop combo is preferable. The combo encourages you to use the devices in ways that play to their respective strenghs. This can be limiting in those moments when you need a laptop but only have an iPad-- and if that happens to you all the time, perhaps the Surface is a better option.But the limitation might make you more productive overall via forced optimization.
The Surface might offer convenience that "iPad + desktop" lacks, but in exchange, it demands that you accept some comrpomises. It's hard to know if "convenience' wiill actually make you that much more productive on the whole. If I'm writing a lengthy artciel, the Surface keyboard is just barelygood enough. I definitely work more slowly than I would on a PC.
The Surface dock is a potentially different story, though. With the Surface Pro attached to a full-size keyboard and monitor, it becomes pretty compelling. It's powerful enough to provide a legitimate desktop experience. Two-in-one convergence hasn't yet proved as popular as Microsoft hoped, but I think the three-in-one concept that docks enable will gain fans.