The conversions matter a lot in the scheme of things. Not as much to a new player, but to your older established base of players.
I guess I'm not really sure why we're talking about conversions here at all, though I must echo Fifth_Element in that I'm doubly unsure why someone wouldn't want classic modules converted to 4E (unless it was to the total exclusion of new, original 4E modules, I suppose).
Ultimately, I just wanna see more adventures! New ones! Old ones remade for 4E! Put 'em in boxes! Put 'em in folios! Give 'em numbers instead of names! I said more or less the same thing on the WotC forums back in early 2007, IIRC, and I guess enough other people must've been saying the same thing, because WotC has gradually started doing just that. Keep it up, Mike!
Even the jump 2E to 3.5E is fairly painless. Homebrewed innate powers translated well to various Feats (Custom in some cases), the proficiencies right to skills. Really the hardest part to overcome was the fact higher was always better now.
So you didn't 'leave behind' too many players, heck you brought quite a number of older players back into the fold of buying the products again. And Mike, himself, is an example of that in his own words.
The jump to 4E brought a lot more change to the D&D world than many cared for. The conversion becomes important in the fact if folks can't easily convert there characters into the new edition, guess what they are going to continue playing the older edition.
Remember that the jump from 2E to 3E was a mechanical one. Suddenly, D&D worked differently, but it still looked the same on top.
OTOH, the jump from 3.5E to 4E included a lot more superficial and flavour changes. This is what most irritated a lot of "haters". The mechanical aspect of that change was fairly subtle, especially for players who had been up-to-date with the incremental changes in 3.5E over its production lifespan. This gradual change is the "hidden edition" between 3.5E and 4E. If you used (for example) Complete Mage's Reserve feats, Book of Nine Swords, Tome of Magic, and Player's Handbook II, the 3.5E you were playing was a lot more like 4E than core 3.5E ever was*, and as explained up-thread, Mike Mearls was a part of this. (*It's said SWSE was yet more similar to 4E even than these products.)
As Brand Manager Mike will be tasked with three things primarily.
1. Bring new players in to buy WotC stuff.
2. Keep the players we have buying WotC stuff.
3. Bring older players back int and buying WotC stuff.
All boiling down to finding out what the market wants and trying to fill that need.
Is that Mike's new title, "Brand Manager"? I heard something about being "Manager" of D&D R&D, but are you sure you've got his new job description correct? I'm confused.
No they learn them from their fellow players. I've yet to pick up a 4E book to learn the rules of the game. Yet I've successfully handled playing just on the basises of my fellow players explaining a few finer points to me.
You mentioned that you were a "4e hater" earlier. Is it possible that your negative attitude towards it is due to attitudes that you learned from the people who taught you to play 4E?
I'll be less rhetorical: having studied some social psychology, I know that science says it's definitely possible that you did. Have you considered picking up the books? If you approach it with a fresh mind, you might find a new appreciation for Mike's work.
I'm excited about the way D&D is going these past few years! I think Mike is the right guy for the job today. And personally, as a 4E fan who is aware of Mr Mearls' strong influence on the recent direction of D&D, I'm growing interested in checking out this "Iron Heroes" thing he worked on previously. Since I like 4E, maybe I'll like Iron Heroes too.