I have read T-mag from the very beginning and lurked the forums daily as well. Finally decided to add something to the great site that has become the foundation of my training knowledge.
Anyway I have often used lunges in my routines as a squat replacement for short periods with great results. Whenever my low back is injured or overtrained it becomes the core of my leg routine.
Well my wife has always had a terrible time with barbell lunges and when she recently injured her low back I set her up doing smith machine lunges because she couldn't balance well enough to allow enough load on barbell lunges. Within a few weeks of smith machine lunges she tried doing barbell lunges and found she had overcome her balance issues.
Her last workout she used 135 for 6 sets of 8 with the barbell when before 65 was a struggle even when her squat strength was in the 145 for ten range.
Several times in the past she had tried dillegently to improve her barbell lunges with light barbells and dumbells with no real improvement and alot of frustration but after a few weeks of using the smith machine she was able to improve tremendously.
Anyway for any of you that might might like to include heavy barbell lunges but have had trouble with them in the past or any beginners just starting the lift and having trouble, using the smith machine for a brief period might unlock one of the best leg exercises out there.