One of the reasons I enjoy reviewing open source software so much is because the process is so much simpler — find program, download program, use program, write about program, rinse, repeat, etc. Going through commercial companies to get software and review it can be much more difficult and painful — but, as with any situation that is annoying at the time, you usually get a good story out of it. And that’s important too. 
David Pogue shares a few of those stories over on the New York Times Web site in his “Amusing Tales of Product Managers.” My favorite is the story of the company that keeps adding features to a product to tailor the software to his liking prior to the review — to wind up with a version 1.1.1.1.1 release.
Also brings up an interesting question — how much give and take should one have with a product manager as a member of the press? Usually, I won’t share much with a company or project before the review is published, but sometimes it seems unfair to keep the programmers in the dark completely — especially if it’s possible that you’re missing something or there’s a reason why feature XYZ isn’t working on a particular setup. (This is especially true when writing about software for the Linux desktop, and your setup could vary drastically from the expected installation candidate.)
