Disk, not CPU, has been the performance barrier for much of computing. Largely because of latency (from seek), which as yesterday's HN article noted, is something you're stuck with.
You can increase your CPU capacity through palatalization (up to Amdahl's limit), but disk sucks no matter what. Yes, with multiple channels you get better overall throughput, but if you need two blocks that aren't contiguous but are on the same media, you've just bought an eternity in compute time.
SSD cracks that barrier, and does it pretty spectactularly, so yes, it's been a pretty big breakthrough.
The next phase may well be localization of a lot of services which are now centrally web-hosted. While in aggregate, people need a lot of compute power, individually, it's not much, and tools such as the FreedomBox offer the opportunity to put that close to you, while distributing data for both data integrity and thwarting surveillance (it's tough to run centralized surveillance over a decentralized architecture).
Round-trip time for SAAS is itself significant, as is browser load. Cracking both these nuts for the ultimate in edge-provisioned networks (the wall wart 6 feet from where you sit), and a movement away from browser-based apps to a lighter-weight frameworks which is based on network transport but doesn't impose a full browser overhead.
