The DS Compatibility Databases have been in operation since 2005 and provide continually updated compatibility information (only the English games) including save types and other settings, problems (sometimes solutions), some video samples, etc ... along with live help (not 24 hours daily as the main crew are in similar time zones)
The crew have so far found 8 new games are now playable with 2.6a (one of which has not previously been playable with any emulator), one game no longer playable with this version while one game has been upgraded from initially playable to playable
They've recently added total (using all the emulators and versions) playability stats (these get updated with each database update) : 91.41% of the English games are playable (or fully playable), 3.78% are fairly playable, 2.92% have a lesser playability ranking and 1.89% are not playable ... there's also a database showing which emulator is best for each game
The latest stats can be found via their javachat (or irc) with the !stats command at
http://www.dscompatibilitydatabases.co.nr/
I believe the latest stats for No$GBA (not just 2.6a) are 87.29% are playable (or fully playable), 3.95% are fairly playable, 4.12% have a lesser playability ranking and 4.64% are not playable ... retesting for this version has not yet finished (although most of the problem games have been retested)
Their small crew put in a huge effort to keep the data up to date, work on other related projects and I've seen them help a lot of people with problems
I know they'd like to hear from any serious game players (as obviously they can't test every game to completion) if anyone is interested