I was afraid of weight gain with insulin, but I've lost alot while on it (near 80 lbs).
Instead of taking insulin to cover my carbs, I ate carbs to cover my insulin. My goal was to reduce the amount of insulin I needed instead of increasing it. The only way that I know of to do that was decrease my carb intake.
I used 60 grams of carb per day as my bench mark. Not only that, I made sure that those were low GI carbs with the occasional medium GI carbs.
As the weight came off, which was rather rapidly in the beginning, I was able to decrease my lantus intake significantly without actually having to reduce the carb intake. In fact, I've been able to increase the carb intake. I suppose that's the whole insulin resistance thing. It decreased as my fat decreased.