1. HTTP Pipeline support proved very difficult to implement reliably; so much so that Opera was the only major browser to turn it on. It can be enabled in Chrome and Firefox but expect glitches. By all accounts SPDY's framing structure is far easier to reliably implement.
2. WIth SPDY, it's not just the content that's compressed but the HTTP headers themselves. When you look at the size of a lot of URLs and cookies that get passed back and forth, that's not a insignificant amount of data. And since it's text, it compresses quite well.
3. SSL is required for SPDY because the capability is negotiated in a TLS extension. Many people would argue that if this gets more sites to use SSL by default, that's a Good Thing.
4. If you're running SPDY, the practice of "spreading" site content across multiple hostnames, which improves performance with normal HTTP sites, actually works against you, since the browser still has to open a new TCP connection for each hostname. This is an implementation issue more than an issue with the protocol itself; I expect web developers to adjust their sites accordingly once client adoption rates increase.
5. The biggest gains you can get from SPDY, which few have implemented, is the server push and hint capability; this allows the server to send an inline resource to a browser before the client knows it needs it (i.e. before HTML or CSS is processed by the browser).
But as someone else as pointed out, the author's test isn't really valid, as he didn't test directly to sites that support SPDY natively, he went through a proxy.
The website I work for is supporting SPDY, and the gains we've seen are pretty close to the ~20-25% benchmarks reported by others. As many have pointed out, this author's methodology is way broken. I'd recommend testing to sites that are known to support SPDY (the best-known are Google and Twitter), with the capability enabled and then disabled (You can set this in Firefox's about:config, Chrome requires a command line lauch with --use-spdy=false in order to do this, though).