There have been many such quotes from both multi-platform and exclusive PS3 developers. The main issue is that it takes some time and effort redesigning legacy game engine to use the Cell's multi-processor CPU design well enough. These issues do not apply to game engines designed from scratch for the PS3 and Insomniac appears to have fully redesigned their legacy game engine for Resistance 2 already, running nearly everything on the SPEs instead of on the PPE. It seems to have been a pretty straight forward process for them. They actually accomplished this faster than I thought would be the case back in 2005.
The main issues remain with legacy game engines which haven't been adapted that much, mostly those who claim difficulties either use middleware which don't use the SPEs well enough or some who seem unwilling to adapt (Valve). Middleware designers I believe usually don't criticize the PS3's architecture as they know their technology hasn't been adapted well enough to suit the PS3 in such cases, those devs who are using their technology are often high level developers lacking a deep enough understanding of the hardware. It would be a little like user designed levels created with a level editor, you need to have no great in depth knowledge of the underlying hardware to create such content, you mainly need knowledge of the provided tools.
Most developers agree, the PS3 is a lot easier to develop for than for the PS2. Due to their differences 360 ports would be inefficient without significant adaptation (I know the devs who had to adapt DirectX games for similar specced Mac, Amiga and Linux, they had to go through quite a few ordeals as well, a straight port would be horrible, but the end result with significant adaptation was actually far more efficient) , porting from PS3 to 360 isn't an issue at all as the PS3 requires smart coding which indirectly even helps the quality of PC/360 porting!