I have used Levemir for over a year now. I was using Lantus before that, and I was getting inconsistent bg levels...specifically the fasting ones. I was taking 12-15 U Lantus at bed; I now take 12 U Levemir at bed. My levels have been much more consistent.
I am 43 and have had diabetes 10 years. I'm in the Type 1.5 and/or LADA category....definitely not Type 2.
I can't say that the Levemir itself caused weight gain. In the 10 years, I probably have gained 10 pounds. I do think insulins in general cause weight gain, and in my opinion make it more difficult to lose weight. That is why I try to eat lower calorie meals and exercise. Even with non-diabetics, if meals are high in calories and there is no exercise, that person will gain weight. It's just a bigger challenge with diabetics.
To get back to the point, I do like Levemir much more than Lantus. Hope this helps....