Contrary to AMD's claims at launch, all Phenoms are affected by a system-halting data-corrupting bug known as Erratum 298. The only way to fix it is an update which disables part of the L3 cache, causing a 40-50% drop in L3 performance. This translates to an average 14% drop in real-world performance, up to 50% in programs like Firefox.
Also, it was discovered that AMD had sent overclocked processors to reviewers, which artificially made the Phenom look more competitive to Intel's Core 2 Quad. Some may see this as being an even bigger issue, as it makes AMD look insincere.