Do You Lunge, And Why, Why Not?

I don't want to jinx myself, but after three years :) , lunging Rogo finally seems to be coming together for me. I started lunging him the fall he was three and a half. Boy, he sure didn't think that was a good idea. I mean, why would we do that? We could just hang out and eat carrots while I scratched him so why would he run around in circles? Duh. The lack of interest in participating in this new activity manifested itself in him running away from me, and I lacked the finesse and experience to hold him. Bad start and bad habit learned. If he did stay with me, he'd just come to a halt whenever I asked for a trot (forget canter for another year). A few steps of trot earned a "good boy" and carrots. It was the only way to get him to do it. To this day he pauses with a hitch if I say good boy when riding, muscle memory of a carrot appearing next.
Doug got involved in this too, poor guy. When I couldn't hold Rogo he took over. I can still see Rogo cantering down the ring with Doug's heels dug in sliding along behind him. So he built a small pen to lunge him in and on it went. You get the picture. Rogo's lack of interest in working early on could make up several posts, and no doubt I'll do one or two sometime, but this post is about lunging. (Just a quick note on it though - we didn't ever 'force' him and patience was the key.)
I myself wasn't strong in the skill of lunging, having only lunged trained horses, and lunging correctly is a real skill. Without supervision I let Rogo flop around on the lunge line without really working, just happy he was going forward. This went on for too long. If I pushed him he ran away and I got in the habit of not pushing and also to be honest I didn't really know what I was looking for or should be asking for. Sometimes I'd put the lunge line through his bit on one side, around his poll, and attach to the bit on the other side. I can hold him this way, but it isn't a very good training method.
I didn't want to use side reins because I see SOOO many horses behind the vertical and I was afriad that without skilled supervision I'd over do it. On it went, Rogo happily flopping around on his forehand (not that lack of side reins equals this - I mean the whole picture).
I had a teacher for a time who was skilled at lunging, but although I'd watch in admiration I couldn't produce what she did with him. There's an element of feel, confidence and knowing what you're after and how to get it that I just didn't have.
Cut to this summer. Rogo was still running away from me on and off and one day I HAD it (dangerous, etc., I posted about it). With the determination born of needing to cure a dangerous habit I put him to work. I used the lunge line around the poll method and side reins to keep him with me, and I pushed him out of his work comfort zone into a BIG trot. Rogo's not big on big trot's, although he has a beauty when he does it. We did this a few times until he stopped running from me, and then I went back to not lunging. I kind of missed the break through - I was teaching him the gait I wanted, which I couldn't seem to do as effectively or quickly mounted.
Currently coming back from a period of low to no work (Rogo's cut leg, my 'down' time) I was faced with a very lazy horse and a low energy me, so I turned to lunging. OMG - I think I've got it. I'm fastening the line on the side, using side reins at times (I've used them enough that he understands and is ready) without under or over doing it, getting a big, forward trot, and the trot it carrying over to mounted work. In yesterday's ride he carried the trot of my dreams after lunging, something I can work on for 30 minutes and not get if I try it mounted without lunging. Without lunging, there are days I can give him 3 good solid whacks with the whip and still get just a half hearted, short response. This leaves me feeling really yukky (it's like whipping a sweet puppy frankly, and it does no good). Who wants to spend their riding time like that, or have a relationship like that with their horse? Not me.
So, fingers crossed, I think I have a good tool I can use effectively finally. I'm not mean to him on the lunge line (pushing too hard or 'chasing' him). It's just as though we both get it now - focused and forward. Rogo isn't the least bit upset or reluctant. He's as happy as can be and enjoying himself. Is he the equine equivalent of the person who says "I find it hard to go to the gym, but when I get started I love it"?
So, here I am, lunging to put an edge on :) I know many people lunge to take the edge off. Also, some trainers don't think lunging should be used, or used very sparingly. I'm very interested in knowing what you think of lunging as a training tool and / or if and how you use lunging.