Electronic cigarettes are a novel invention, that's for sure. I have some, and tried using them to quit smoking cigarettes a number of times, but failed horribly. Sure, it contains nicotine, it looks like you're exhaling smoke, but it still doesn't feel the same to me. It lacks that throat hit that comes with puffing on a real cigarette. Personally they didn't work out as well as I'd hoped in regards to replacing regular cigarettes, but if you succesfully get them to work for you in that manner, than i applaud you.
I'm not realy sure of your question, though.. You're asking if e-cigarettes help with treating ADD? Well you said so yourself, that 'between the cig and caffeine I feel way better". So if you have found something, or a combination of two things, that works for you, without going the amphetamine route, than I would say there's no reason to change your routine. Caffine and nicotine are both stimulants, though obviously have different modes of action than an amphetamine type drug would.