Have you confirmed that the command doesn't work with the 1.0 - 1.4 exes?, it may have been inactive.
Perhaps a test with 1.5 geck and 1.0 game is due.
I just checked the Tesla Canon with both 1.5 and 1.0.0.15 and it seems the chain lightning effect
does, in fact, work with both. If two or three Raiders were close to each other, the effect was that the projectile appeared to arc to the next target and so on, both with 1.5.0.22 and 1.0.0.15. I'm not sure if it means everything will work with 1.0.0.15, but in a crowd of Raiders with both exe's, I was getting multiple kills per shot. I didn't see any difference.
Fallout3.exe causes those crashes. If you run v1.0.15 with essentially the same Fallout3.esm (thanks to JustinOther's Fake Patch) you should experience any crashes on saving.
Cipscis
I love 1.0.0.15 for that. It does seem as though they've fixed Alt+Tab for 1.5.0.22, on the bright side. While testing the Tesla Canon, I'd forgotten which .exe I was currently using once and mistakenly thought it was 1.0.0.15 since it actually let me back in, but lo and behold, 1.5.0.22 also letting me in and out consistently, however hanging on exit forcing ye olden Ctrl+Alt+Del -__-