One of my favorite things about it is the way it handles memory during debug runs. (My #1 favorite thing is that it was all developed by one guy working solo - Brian Fiete, a cofounder of PopCap Games.) First, it's able to trace allocated memory during debug execution and immediately report on memory leaks, along with the location in code where the leaked memory was allocated. Second, it can guard against use-after-frees in debug by marking the memory freed, but not actually reclaiming it. Any subsequent writes/reads to that location will immediately fail with the object's allocation stack trace.
Both of these are turned off during normal builds but seem to be excellent debugging tools.
The IDE is also cool and was developed in conjunction with the language. It's not the most feature-rich application and there are some bugs as you'd expect, but it's a perfect example of dogfooding as it was written in Beef. Hot code reloading is also supported.
Note that I have zero connection with this language, other than that I really enjoy it so far, and that I reported a minor issue that is probably very specific to me and me alone, and Brian replied to me personally and we had a pleasant brief exchange.