I bought this game for $5 at KMart several months ago and I STILL feel ripped off. Not only is the gameplay short, dull, and repetitive, but it's also extremely gimped on content and gets most of its replay value from having to beat all the lame missions with every sub to unlock the last few missions. I tried getting to that point, but while I was clearing my way through with the second or third sub, I realized that I had so many better 3DS games I haven't finished that I could be playing and that Steel Diver was a complete waste of my life.
Some people might like it, some people might not care that it's five bucks down the drain, but I would advise the people who buy games for fun and not just because of a cheap price point to avoid this title. There's more offensive shovelware out there, but with as many stellar titles as the 3DS has, this one isn't even worth time time it takes to pop the cartridge in.