I've had very limited success with the S4A extension so far.
Mac OSX 10.9.5 - Analog Pong and Blink work. LB_S4AFirmware.ino loads. Scratch (S4A) finds board, but only lights d1/tx (d0/rx remains off). The input a.0 shows the pot value in S4A, but will not send to d9 through S4A to the Number bit. I also am not able to set a5 values on the Bright LED.
Windows 7 Pro SP1 64bit (two systems) & 8.1 Pro 64bit - Analog Pong and Blink work. LB_S4AFirmware.ino loads. Scratch (S4A) says searching (even if assign the board manually to the serial port), yet it only lights d1/tx briefly. The input a.0 shows the pot value in S4A for a second if I disconnect the Arduino unit. Tried changing COM from 3 to 5. No change.
Linux Mint 17 64bit - Analog Pong, Blink, and S4A worked. Both d0/rx and d1/tx lit, could send pot value to a9 and turn on LED through a5. However, the S4A deb install made Linux inoperable after reboot (if you look at details on S4A15.deb, it has a list of things it will uninstall, including Cinnamon and Nemo). No worries. I needed to test Linux Mint 17.1 anyway
Also, in Mac and PC, it doesn't seem like S4A is loading the correct S4A.image file. It shows the Arduino littleBits image and logic briefly, and then reverts to the default Arduino unit (Base S4A). If I load the littleBits example SB manually afterwards, it changes to the correct sprite. To be clear, in Windows for example, I double click on the example and it fires S4A, asking me to select an image. I select the littleBits image from Git Hub, it shows the correct module briefly, then reverts to the default and does not load the example SB file. I have to manually load the file.