The game looks great, has tons of content (near equivalent to the recent XBLA release, Worms 2: Armageddon), and doesn't cost a whole lot of money ($5). There are, however, a handful of niggling complaints that could be made about the lack of precision control necessary for a time-based game, as well as long load times strewn throughout the game's menus. Unfortunately, these little issues add up to a much bigger one -- they make me not want to play the game.
The slowdown of the game sometimes drove me nuts; I ended up turning off the sound for what seemed to be an increase in general performance. As I've stated in previous iPhone It In's, I'm using an iPhone 3G, so your mileage may vary.
Control-wise, things got messy when I attempted to do anything too quickly. Double jumps require a double tap on the screen, though due to the control system's unforgiving sensitivity, I often sent my worm single-jumping to his death instead of backflipping to a higher ledge. And while the timer ticked down (with less time for each subsequent level), the aiming reticle was deviously hidden behind my thumb, never precise enough to give me confidence in any shot (other than blanket bombings, of course).
In fairness, it's a fully featured iteration of Worms with 50 challenges, four-person multiplayer and a "quick play" mode for when you're on the go (though my load times were still a bit cumbersome) -- for only $5. That being said, as much as I enjoy Worms games, I very much doubt I'll pick this up again.