First, I continue to be a big fan of Jim McLean as an instructor, he has a many fine video's available at no cost on YouTube. I do think the video Rusty offered above needs some caveats as it differs from many instructional materials. In his 8 Step Book, McLean separates swing types into 2 types: a) arm swingers and b) body swingers. Fred Couples is an arm swinger, as are most junior golfers, they swing with minimal body effort (I am an arm swinger trying to become more of a body swinger). Most tour golfers ie Nicklaus, Trevino, Sergio etc are body swingers in that they use the large body muscles and movements to power the swing. So, to my thinking, there is value in the video regarding how to swing your arms and/or how to teach a better swing to those with bodies less supple than they were in youth. But, for sure, it is not a simple fix for the great majority of golf swings.
Could you expand a little more on how the Haney video's focus on your particular problems to find the one or two things that can produce faster improvement.? I've taken several on the "on-line" questionnaires to find a quick fix, never been happy with the choice of questions or the proposed improvement. BTW, most teaching pros will tell you that if they ever try to change a grip on the first lesson, they will never see the student again. So good on you for making a grip change, there are so many golfers who play with crappy grips. I, too, have watched Haney on the Golf Channel, he professes to teach, first, an on-plane swing...which is a very good thing. If you like the improvement to-date, the cost is minimal. Are there recurring monthly costs to continue?
My personal favorite golf instruction series is the Golf Channel's School Of Golf with Martin Hall. Last night, the episode was titled "Geometry of the Golf Swing" and delt with the on-plane swing. His simple test(s) of very quickly convinced me that I an swinging too much inside to outside - a long standing issue in my swing. I intend to work on this in the next 2 days, I'll revisit this tread and announce how it went.
The paradox of golf instruction is we all want better ball flight, pro's can only teach us better movement patterns.