Depends on how you define "stable".
Stable by any mean should be the CM7.1.
Anything else is "pretty stable" based on my definition.
Official CM10.1 Nightly @ 1000MHz NOOKcolor
Offiical CM11 KK Nightly on Kindle Fire 1st-Gen
Rooted Kindle Fire HD 8.9" w/ Nova Launcher
Virgin JB 4.3 on Sony Xperia Tablet Z
Rooted stock-ROM KK 4.4.2 on LG-D800
Virgin Samsung Galaxy Tab 2 10.1 - LOST
Slimbean 8.1 on Galaxy S2 i777 - LOST