Well, I seem to have missed this thread so far. Anyway, just some thoughts looking at it.
Quick Tentacle: You might want to change the 15 foot reach to a 10 foot increase in reach, for those that are either large or have taken pains to increase their normal reach above 5 feet.
Also, I may be reading it wrong, but it looks like the base damage of the tentacle is 1d6 per class level, which seems a bit high for its progression.

As for adding options, you could try adding in some abilities where you can choose between choices oriented toward more combat focused use of the tentacle and more utility focused use.