I was taking 100mg and am currently upping my dose to 150mg - slowly because I'm ultra sensitive to medications. I'm increasing it by 25mg for 2 weeks, then 50mg.
Spaced out or numb? Not at all.
Weight gain? Nope. I've lost weight.
Feel better? Absolutely. Huge, huge, huge improvement. And it starts to work quickly. I've had zero side effects - quite a feat for me. If I miss a dose, I do get spacey and light headed, but it goes away within an hour or two of taking it.
You do increase slowly: 25mg for 2 weeks, 50mg for 2 weeks, 100mg for 2 weeks, then 200mg. 200mg is the therapeutic dose, but I was holding at 100mg because it worked for me. I've recently needed an adjustment. My doctor said she would normally go straight from 100mg to 200mg, but she knows how sensitive I am to medications.
The one thing you need to keep in mind - besides the Stevens Johnson rash, which is one of the reasons you increase slowly - is that if you stop taking it cold turkey, it could induce seizures. You would have to taper off.
I love it, though. It's been a lifesaver for me. I really want difficult child 2 to be on it, but his most recent psychiatrist is being difficult.
ETA: It can cause insomnia. I take it in the morning. It can also be sedating, in which case you would want to take it in the evening. You would have to see how it effects you. Some people take a split dose.