Well, the question is pretty obvious...is Streamline still the best PCB mod? Are there any others that are better / more recent? (it's a bit outdated...the latest version is the 3.1 Open Beta, from Oct 2008)

Also, another related question. I plan to run it along with Oblivion Stutter Remover. Is anybody trying 4.1.26 WIP? Is it stable / good for general use?

All of the other PCB mods that I am aware of are older than Streamline.
OSR 4.1.246 is stable, but you will still need to play with the settings to find what works best for your system.

I use http://www.tesnexus.com/downloads/file.php?id=9139 with the newest OSR. Never any problems.

There is also this one by kuertee.(I use this version now instead of Streamline.)

http://tesnexus.com/downloads/file.php?id=22136

I can't speak to "the best." I can only describe the one I use.

http://www.tesnexus.com/downloads/file.php?id=27009 will not purge the buffer during combat. It will only purge after a set time and/or visit to a specified number of unique cells that the user sets in its INI file. These work well for me.

Old (or "old" rather) doesn't necessarily mean outdated.

Another option is Map Marker Overhaul. It will do a PCB on demand or when you fast travel. Since I frequently fast travel, it's the best solution for me.