It isn't free, but it is supposed to take less system resources than any other antivirus and is still in the top 3 for detection rates, especially the important category of 'heuristic detection' which is used to detect new viruses not yet in the database.
So I tried it out. It actually seemed like it would deliver. The memory usage was very low, at least.
However ever since this 'reformat', BW would have random spikes of lag. This seemed to mostly happen when a sound effect played, but it was very irritating. Basically a 0.5 second period of frame stutter.
It took me a little while to figure out it was NOD32 at fault, but last night I uninstalled it and put Avast Antivirus back on. The lag spikes disappeared.
NOD32 is not BW friendly.
Edit: Several people have replied that they have had no issues with NOD32 and BW, so YMMV. For me it was certainly the cause, but as always it could have just been 1 part of a multi-piece combination that ruined me.