I've used D's GC with DDMD. It works*, but you're trading better memory usage for worse allocation speed. It's quite possible we could add a switch to ddmd to enable the GC.
As a random d-user (who cares about perf/speed and just happened to read this) a switch sounds VERY good to me. I don't want to pay the price of GC because of some low-end machines. Memory is really cheap these days and pretty much every machine is 64-bits (even phones are trasitioning fast to 64-bits).
Also, I wanted to add that freeing (at least to the OS (does this apply to GC?)) isn't exactly free either. Infact it can be more costly than mallocing. Here's enlightening article: https://randomascii.wordpress.com/2014/12/10/hidden-costs-of-memory-allocation/
