Even now, after almost 10 years of programming, I still wish my debuggers had arrows pointing to data structures in a nice GUI. Sometimes, you don't want to interrupt your train of thought to recall the gdb or pdb command you need, or to remember "was 0xAE32F542 the first node in the list or the second node?" And consider the WebKit debugger for Javascript: just by looking at the Scope Variables tag, it's not obvious to catch a bug where you did `x = y` rather than `x = deepClone(y)`.
TL;DR I wish this was the same as a debugger, because then debuggers would be awesome.
Not quite. The visualizations are great, but the ability to rewind and replay time is the critical piece here. How many times have you had to stop and restart debugging because you missed something critical?
TL;DR I wish this was the same as a debugger, because then debuggers would be awesome.