Yes, I'm at I think Mission 7 or 8. And even then I just barely skimmed past a few of them. Like I said, artillery confuses me, I know they're an indirect attack unit, but for some reason I just can't attack units that are only a few squares in front, it's kinda annoying. But if I REALLY get stuck, my flash cart has cheats programmed for most games in it, so I'll just use that to get past a level I'm stuck on.
You will need it for Mission 20... And for a few others.
They are 2-3 Range, right? And if possible, I usually substitute Artillery with Rocket Launchers.
Most of the games I'm stoked for have been out for years.