I guess I don't like more and more "special signs" (like @, [], <>, #) invading the code.
I've witnessed it with Java where a lot of new syntax was introduced. The thing is, these are all new concepts adding to the complexity of the language (annotations, generics,...). I prefer to keep things simple.
It's really quite elegant if you think about it. It's a highly dynamic language that was designed more than 20 years ago and is still very relevant today as the platform of choice for developing nearly all Mac OS X and iPhone apps. As far as dynamic languages go it's very fast since it's compiled. It integrates seamlessly with C (and even C++).
Just because you don't know or care about Objective-C doesn't mean there aren't plenty of people who do. I regularly see articles about Objective-C on the front page of Hacker News, Reddit, etc.
Therefore although their effort with what they call Objective-J may be worthwhile, it's certain it will never go mainstream.
One significant reason? It runs toooo slow on IE. IF it ever gets fast, maybe more people will give it a shot.
And it's certainly not stopping people from writing apps. There's now more than 10,000 apps on the iPhone App Store alone.
Mechanics have wrenches with the edges ground off or thinned down, even heated and bent to fit special applications. So why shouldn't I have my own syntax which sits on top of a readily available platform?