I came within a nager's breadth of buying Mercs 2 a short while ago, and many of the reasons as to why I didn't buy it were pretty much summed up in Yahtzee's review.
Although channelling most open-world games to an extent is fine, it needs decent AI to back it up. Add to that unrealisticly forgiving/punishing physics and some of the worst voice acting I've ever heard and, well, I can't feel the slightest bit glad I skipped this and decided to reserve a clutch of games that've got me all hot and steamy.
Like Far Cry 2.
*Shiver*