Have you ever tried running Office with a little network latency? The 10x slowdown is barely usable and unavoidably annoying, especially if you're used to a faster computer.
Maybe we just have really fast networks.
I assumed he meant something where the network latency would impose a keystroke-level degredation in performance.
The picture may not be that grim if at least timing-critical parts of Office can be made into fat binaries. I would not bet on straight emulation of uncooperative code, however.