Well once its in the svn ... it is pretty much *official* though as you saw is subject to modifications.
In general besides strict ana it pretty much is exactly what you are running if you followed my previous suggestions. So rock on!
fast decomb vs. decomb default (known internally as decomb 2 and decomb 3) vary in terms of speed as to what machine you are using. Basically on a fully progressive (24 fps source) fast decomb has virtually no speed hit even on a 2006 mbp running a slow 2.16 c2d . Of course once it want to deinterlace it will then slow down. decomb default (decomb 3) uses a more exact scan of each frame which is more accurate in some cases but slows HB down even on fully progressive (24 fps) sources. So even if decomb 3 (default) never has to actually deinterlace or blend a frame, it has a speed hit just in trying to detect combing.
That said and this not an official HB position but imo I have had fantastic luck using fast decomb on *everything*. yes, it might miss a frame or two but in general it rocks as fast as not decomb and I rarely see misses. Again as always .. ymmv.
Note: we are planning on optimizing decomb 3 ( decomb default) upon which in my commit notes it will be then default on *all* built in presets. Note upon note: I have always pushed for decomb fast to be in all built in's for at least three years. imo decomb fast is much better than no decomb even with its margin of error. But thats another story ....