I take Lithium and I personally think it really helps keep me stable. I have been on it for years.
All meds have side effects, you just have to decide which ones you want to deal with.
I did not gain any weight, but I did have a tremor and was thirsty all the time when I started. They went away in time.

My thyroid has been affected so I have to take thyroid meds.
I have my kidneys checked 2 times a year.
I have my lithium blood levels taken every 3 months unless I am changing the dose or have gotten into the toxicity range.
I have experienced toxicity a couple times, but I recognized the symptoms and called my pdoc (I was having major GI problems, both ends!)
I drink alot of water every day and make sure I don't get dehydrated. I also tend to use less salt.

I think Lithium gets a bad rap because most people don't understand it.
I think the anti-psychotics are worse as medications because some of them cause tremendous weight gain and metabolic disorders like diabetes.
All meds have side effects, just need to decide which ones you are willing to deal with..Good luck.