I'm highly skeptical of quantum computers. I mean, they may be possible on football field-sized scales and available only to the top government agencies for cracking codes -- but I just don't feel that they could be miniaturized enough to be practical at home in the foreseeable future. They are extremely touchy and fragile by their very nature (even a tiniest disturbance can result in decoherence and loss of all information), they are extremely hard to maintain, they can only maintain memory for extremely small time periods, etc, etc, etc.
But even more importantly, they are not suited for the typical essentially deterministic tasks we expect computers to perform. For example, quantum computers are absolutely useless when it comes to word processing or web browsing, or rendering 3D virtual reality scenes. Computers as we know them today are universal, easily programmable machines. Quantum computers are not even close to achieving such a status. Even though there is a chance they might make it, or at least eventually supplement classical computers with quantum-parallel "co-processors", I wouldn't hold my breath over the next few decades.
The hard disks are indeed advancing by leaps and bounds, but they are rapidly approaching physical limits. They are also power-intensive, mechanical, and two-dimensional. Personally, I think the future lies in 3D holographic memory "crystals".
Also, a potentially revolutionary technology with lots of promise is high-temperature superconductors. Just imagine circuitry that dissipates no heat -- the maximum attainable clock frequencies could probably jump a few orders of magnitude right there. Imagine handhelds and laptops a million times faster than today's fastest desktop, and lasting for weeks and months on their batteries instead of just hours.
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I am; therefore I think.
[This message has been edited by Boris (edited October 28, 1999).]