I suggest you go away and read the Google Breakpad project web pages. Your questions require me to give you information you'd already have, and to explain why your question is confused because of the lack of that information.
What experience you have with using it?
None whatsoever. But that is irrelevant, if you understand Google Breakpad and have read the pages -- because I've used Window's minidumps before.
How hard is to integrate it into existing code base.
Simple. It took very little time.
How useful information provided by Breakpad is, compared to GDB?
Answered in project web pages, and confused.
What overhead it has e.g. library size?
Answered in project web pages. No idea on Linux, but project web pages will explain why it will likely be higher on Linux. Regardless, I expect it to be a nominal amount. All it has to do is capture stack frames for the executable you distribute (and associated information).
I'm asking since I learned about this tool for first time here (I have been lurking around for some time, just didn't register before) and it looks useful. It is hard to replicate event in roguelikes thanks to randomization, core dumps would help here, but expecting normal/casual user of being able to obtain core dump is asking way too much. Even then, size of core dump can be huge, which doesn't help reporting either.
People submit save files for Incursion. These are infinitely more valuable than the frozen execution state which a *nix coredump or a Windows minidump would ever provide.
This question is also irrelevant, esp. with regard to size of core dumps, and reasons why are detailed on the project web pages.
The core point is that it's all straightforward and the project web pages are clear on all these details. At least, my basic skimming of them gave me all the answers to these questions, and the understanding necessary for knowing why some of these questions were irrelevant. Yes, I could answer them going back to check and quote bits and pieces, but I don't have the time.
If you read the project web pages and come back with questions, having clarified your misunderstandings, then I am happy to answer questions from that point.
