I don't know a great deal about cars (yet), but I did a lot of reading around on this of late and have just signed up to see if anyone has been thinking along the same lines as me. The top topic in the Honda section is this! Clearly it was meant to be!
Anyway, I found this, which is a great explanation of how iVTEC works:
http://asia.vtec.net/article/k20a/
The technology is exactly as you describe. 30mpg at low revs, a smooth motor that feels like a straight 6, every people who
know cars that I've given lifts to are very impressed that it's just a straight 4. The premise is maximum fuel economy and even performance across the rev and driving styles.
As a result, the engine has many stages of intake/exhaust settings on the valves which respond to driving style "intelligently". Therefore it's dependant on how it's
driven. For over taking on motorways and A roads, down shifting to 2nd or 3rd, the engine kicks like a beast and sounds phenomenal with the textbook VTEC winy grunt. At moments like that, I truly love this motor. But this particular engine is sluggish to get going for sure (especially if like me you're in the tourer/estate :blink

.
But from my reading around, it seems you can modify air intake position and filters, whilst relatively inexpensive, doesn't really yield a great difference. Or I guess the mapping you discuss above. That does seem the more effective option, but still a tricky and relatively costly procedure.
I wonder if the sad truth is that we're driving a beastly 2.4 that you should be able to tune/map very highly, but can't. I mean it's currently set to about 180 or 190 bhp right? From a 2.4, you should be able to get a lot more power surely? But I think the nature of the iVTEC mean that it will never really reach it's full potential (power wise) without crazy money spent on it. It's an engine designed as much for economy, quiet and smoothness as it is grunt and power. So inevitably there's your compromise.
Anyway, I'll be following this thread if it continues, to see if anything can/is done to give it more grunt from stationary. That would be my main consideration if tweaking the response of the engine.
But to further comment on the whole iVTEC thing. I'm unsure how much I like the "i" aspect in retrospect. Maybe I'm being too simplistic, but in a perfect world I'd keep all the economical features for the low revs (I'm happy when I don't want/need acceleration) and simply set it so that the VTEC
always kicks in around 3500rpm.
I rarely take it above 2000 most of the time. I mean, this car will almost drive itself on the anti-stall in 6th gear around town at 25 mph. I love that, I'll get 425 miles off a tank (super unleaded) when I drive like a granddad. But I'd like to always know when to expect the VTEC. With the "i" I'm never quite sure when it's going to kick in in ernest. I always get it when nicely when down shifting, but feel it's late to respond to upshifting, especially from stationary. Maybe I'm just not a sporty enough or clever enough driver to balance the throttle and gear changes well enough to get the most from the engine. It's just sometimes it goes like stink and sometimes it lags like anything, I'm not aware that I'm doing things differently. Do you know what I mean?