Bulldozer has got a lot of hate mostly because of false advertising and because of a series of blog articles written by AMD marketing people before its launch in 2011, which created very wrong expectations about its characteristics.
The wrong expectations and false advertising have centered on the fact that the first Bulldozer was described as an 8-core CPU, which would easily crush its 4-core competition from Intel (Sandy Bridge).
What the AMD bloggers have forgotten to mention was that the new Bulldozer cores were much weaker than the cores of their previous CPU generations, being able to execute only 2 instructions per cycle, while an Intel core could execute 4 instructions per cycle (and the previous AMD cores could execute 3 instructions per cycle). So a Bulldozer core only had the performance of a single thread of the 2 threads of an Intel core, for multi-threaded tasks, with the additional disadvantage that the resources of 2 AMD cores could not be allocated to a single thread when the second core of a module was idle.
So an 8-core Bulldozer could barely match the multi-threaded performance of a 4-core Sandy Bridge, while being much slower on single-thread tasks.
If one would have known since the beginning that the Bulldozer cores had been intentionally designed to be much weaker than the old AMD cores and than the Intel cores, this would not have been a surprise and everybody for whom the price/performance ratio was more important than the performance would have been happy to buy Bulldozer CPUs.
However, after many months during which AMD claimed that their supposedly 8-core CPU will be better than any other CPU with less cores, there was a huge disappointment caused by the first tests after launch, which immediately revealed the pathetic performance of the new cores, which for single-thread tasks were much slower than the previous AMD CPUs.
So all the hate has been caused by the stupid actions of the AMD management and marketing, who lied continuously about Bulldozer, even if they should have thought that this is useless, because the independent benchmarks will reveal the truth immediately after launch.
To set correctly the expectations about Bulldozer vs. Sandy Bridge, what AMD called a 4-module 8-core CPU should have been called a 4-core 8-thread CPU, but which has dynamic allocation inside a core (module in AMD jargon) only for the FPU, while the integer resources are allocated statically. With this correct description there would have been no surprise about the behavior of Bulldozer.
A part of the hate is also due to some engineering decisions whose reasons are a mystery even now, because if you would have queried randomly a thousand of logic design engineers before 2011, all or almost all would have said that they are bad decisions, so it is hard to understand how they could be promoted and approved inside the AMD design teams.
For example, since the Opteron launch in 2003 and until Intel launched Sandy Bridge in 2011, the largest advantage in performance of the AMD CPUs was in the computations with large numbers, because the AMD CPUs could do integer multiplications much faster than the Intel CPUs.
The Intel designers have recognized that this is a problem, and during the 2006-2011 interval they have decreased every year the number of clock cycles required for operations like multiplications and divisions, so that Penryn began to approach the AMD throughput per clock cycle, Nehalem & Westmere matched the AMD throughput, while Sandy Bridge achieved a double throughput in comparison with the old AMD CPUs.
While Intel worked diligently to improve the performance of their cores, what did AMD do ?
Someone at AMD has decided for an unknown reason that there is no need for Bulldozer to keep their existing computational performance, but it is enough to have integer multipliers with a throughput equal to a half of their current throughput and equal to only a quarter of their Sandy Bridge competitor (Intel had announced much in advance, by more than a year before launch, that Sandy Bridge will double the integer multiplication throughput over Nehalem, and it was anyway an obvious trend of the evolution of their previous cores; so the higher performance of the competition could not have been a surprise for the AMD designers).
The downgraded integer multipliers have crippled the performance of the new AMD CPUs for certain applications where their previous CPUs had been the best, while enabling only a negligible reduction in the core area.