I’m not sure the rumored/leaked “Anti-Counterfeiting Trade Agreement” (14MB pdf) is really a trade agreement. The provisions receiving attention make it sound much more like an intellectual property enforcement cooperation agreement. David Post says “it is really about is the tighter enforcement of copyright law on the Net.” Margot Kaminski says it “amps up IP protection and criminal sanctions, without respecting existing international institutional process and involving the interests of developing countries.”
I know nothing about ACTA. If posts from Volokh to Balkinization say it’s bad law, there’s a decent chance it is. I haven’t seen any trade bloggers analyzing the proposed deal.
Trade Diversion 
You likely haven’t seen it because, as you noted, it isn’t about trade at all. Rather, it’s using the guise of a trade agreement to allow the US to expand its intellectual property laws to other nations.
The agreement has a bad reputation amongst civil libertarians and FOSS advocates (two groups with some overlap to be sure) since the agreement has been negotiated in secret and has many worried about the restrictions on personal freedom it would create. From Fair Use limitations to three-strikes laws to the DMCA, many who prefer an unregulated Internet are understandably concerned.
The two links from your post have good summations of the text and proposals. For a more technology-focused view, you might follow some of Ars Technica’s articles. For example, they have an explanation for why they are avoiding the WTO and WIPO for this trade agreement.
http://arstechnica.com/tech-policy/news/2010/03/your-life-will-some-day-end-acta-will-live-on.ars
Some of the criticism has been more hysteria than fact-based, but there are certainly a lot of reasons for criticizing the agreement and the process being used to implement it.
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