if you need the recorder for film business , don't even think about 722 , its not what you need ,
about 744 , you need at least mixer with individual channels out for normal work
i did a couple of shows with mini dv , hdv cameras , with time of the day tc free run , you sync every 3-4 hours , so the tc is must .
the new hdv like cannon already have tc in/out.
the 744 is not 1600 $ jump - its about 2400 with all necessary cabling for every setup work ( of course if you do it your self its only cost of the parts).
for tapping only the 722 is good enough., me i ,need more since usually running the house mix as well and mix the stuff later ,
of course if you do jams for friends , 4 channels are excellent if you have a few other mikes and additional preamp
if you on the budget , the tascam might be better idea then 722 if you use external mixer any way ( i don't sure if it can jam tc or only run external one)
4 gb cards might be enough for for very heavy production day for 2 tracks