360's manufactured after August 2009 may be unmoddable (this includes ones back from Microsoft after that date), but to be 100% sure, it has to be attempted. Wave 4 games are also out which will only boot on Hitachi drives running 1.51 firmware. Other drives must run 1.6 and follow the instructions found on www.xbox-scene.com:

"IF you are on iXtreme 1.6, you can ALSO play Wave 4 and above games, however you need to use a special activation disk to do so. This was added to the firmware specifically for this eventuality - the disk activates "one-shot-boot" mode, essentially it allows iX1.6 to boot any game you insert into the drive, even if its not properly stealthed. You simply insert the disk into the drive, let it spin up (it will say "play DVD"), then swap in your Wave4 game. You will need to do this each time you want to play a Wave 4 (or above) game."

The Unofficial DSTT Kernel V1.17a07 has been added to the downloads section.  If you are having problems with new games not working on your DSTT, this is the kernel for you!