Final Draft for me.
BBC sitcom vs TV sitcom format Page 2
We use Final Draft. It's wonderful. It really allows you to not worry about format at all and get on with it. It has templates from Warner Brothers motion picture to The Bill, including BBC Taped Sitcom, which is what we use.
It's really expensive, but I scammed it by reviewing it for a magazine, then claiming the money back as expenses.
I use Final Draft and have not heard any issues regarding using the BBC sitcom format on it. I think it's a good investment to get this program if you're looking to write long-term.
I started writing screenplays on Final Draft and when I had a go at sitcom, I tried to adjust the screenplay template to match a script I'd downloaded from writers room.
I thought it looked the same but a prodco did comment on the unusual format. Another prodco suggested I just use the BBC Sitcom template that I didn't know existed as I'd never referred to the instruction manual.
I don't think Final Draft is as good as ScriptThing, which is no longer available, but it is pretty much an industry standard. And it does mean you don't have to worry about formatting and can concentrate on the creative side of the job.
And in the scheme of things, it's not that expensive. I became an architectural technician 20 years ago and had to spend over £100 on pens and £40 on a pair of compasses. Final Draft isn't much more than that now.
I use Script Smart; I have no problems with it.