i have proixed them and no they are not worth it at lest for me your dropping range and poison for one extra 1+ S that your gonna need 5 and 6 to hit anyway but i just might be too much of a sucker to poison
But fire can get rid of regen on monsters so your skins can shoot it to hell? COrrect me if im wrong but fire bolas suffer the -1 from long range? ... if so that would be sad...
but i only used them few times unless the miracle faq comes down like for the dark eldar they just seem to miss a lot but if anyone else tried them i would like to know
Its a 1 point upgrade, so the real question is... why not? I run my Terradons in 3s, where I don't really expect anything from the Javelins because the volume of shots is too low. For instance, they need two rounds of shooting, or two units, to get a single poisoned shot. Of course, with the Bolas, you have an equally low chance of wounding something like a Chimera or Abomination or Trolls... but there's still the chance of it happening. That might be something for your opponent to bare in mind.
but if you moved and your not in 3'' of the enemy unit your gonna need 6 anyway to hit which will result in automatic wounds while fire bolas will still need to roll again to wound
The only reason they seem worth it is to negate regen. If you have other answers to regen in your list (laserdon, engine, etc) then I'd go with the poison. Otherwise, these might pay off just by getting that single wound.