Earlier this year in we started to develop a 3D-intensive online game. Some time later we managed to get ourselves a nice little memory leak and turned to the profiler to locate and fix it. This is when we noticed that profiler bundled with FB were a bit inconsistent with readings. One of our team dug deeper and discovered that starting with Flash Player 10.3 the sampler stopped calling function passed through setSamplerCallback function. The bug is logged at https://bugbase.adobe.com/index.cfm?event=bug&id=3006168 and desperately needs votes.
I would like to further explain why this issue is important. The function passed to setSampleCallback should be called when sampler is close to exhausting its sample stream and allows profiler to get the latest profiling data and clear the sample stream. When it doesn't get called and sample stream gets completely exhausted, some profiling data is lost. In theory, this could be circumvented by doing data collection and clearing sample stream manually, let's say every frame. But when you're working with much-toted Molehill API you just have to create a really large number of objects when preparing the scene and here is when it gets ugly. You just can't clear the stream fast enough and you start losing references. Basically, profiler is useless when working with 3D.
I strongly encourage everyone who considers doing 3D or other data-intensive work with Flash/AS3 to vote on the issue.
TL;DR: Profiler is broken with Flash Player 10.3+. Vote on https://bugbase.adobe.com/index.cfm?event=bug&id=3006168 to get it fixed.