Nothing in particular ethandron, but I think its the bitterness of the sloes that seem to make the spirit what it is. You can try other berries if you like but be careful with blackberries, in as ch as don't squash them, or the pips will break.
The amount of sugar that is added to any of these gins is also important. Personally I never add too much sugar, as the resultant spirit can be over-sweet and cloying....add the sugar a little at a time, as once in, you can't take it back out !