I voted "yes" only because I find it nearly impossible to address some questions asked on these forums without in one way, shape, or form talking about a product that I'm not directly familiar with. Yet, to not reply to such questions would be to pass up an opportunity to be helpful based on what I do know about.
Example: Is the PS-1 Grado's best headphone? My answer could have all sorts of qualifications, but from my experience, yes. I've owned only the HP-2 and PS-1, have heard the RS-1 (for sure, several times), the RS-2 and MS-1 (I think), SR-80, SR-60, and quite a few others. But do I really
know these other phones in the Grado lineup? What about the SR-200, or the 225 or 325? I may have heard them at meets I've attended but cannot remember for sure. Even if I did hear them briefly, do I really know anything about them? Not really, but based on reading all sorts of Grado threads at head-fi for 2 years, I can be pretty confident that the field of contenders is pretty well narrowed to the Grado products that I know well. Ah!!! But are there differences between the HP-1 (which I don't know very well) and HP-2 (which I do know well) that could impact my direct answer that, yes, the PS-1 is Grado's best overall headphone?
Another example: Is the SR-71 the best portable amp for $400 or less? Yes, followed by all sorts of explanation based on my experience with the SR-71 and other amps I know well, then all of the qualifications about what I don't know, but the answer is yes. There are many such threads. To not answer based on what you do know based on considerable experience because you do not (and cannot) know about all of the other possibilities would be folly.
I could go on and on, but I've probably bored everyone already, and this is my point! If everytime we reply to a thread we have to provide a headphone resume, complete with footnote explanations providing the dates, times, locations, and systems in which we have heard product X or Y, the forums would quickly turn into a complete mess! Of course nobody is suggesting this. I'm simply exaggerating to make a point.
The simple rule I follow is this: if I can honestly give advice, especially to newbies, based on my experience, then I do so to be helpful. As often as possible, I will qualify my statements carefully, but not ad nausuem to the point that they lose their impact by obscuring the message that I intended to send initially.
But if you asked me if I like the R10's better than the Qualia 010, I could not answer because I've never heard the Qualia 010. I know that jpelg doesn't like them, but then again, what does he know?
(Sorry, Jimmy, I couldn't resist).