Im stuck, I need some sage advice.......
I grew up on a d20 system, and I tend to think in it.  I play it because thats all there is that is out there, but does that mean I must create a new system using the "Industry Standard" of d20.  So I wanted some opinions from fellow designers before I make my choice between d20 and 2d10.

Reasons behind the difficult choice.
by using two dice I gain a bell curve instead of a straight 5% for each number allowing me the ability to tailor make creatures for my PC's. It lets me make fumbles more spectacular, and crits even more spectacular. It helps out the PC's that have poor luck with dice

For those of you that game do you like the d20 system? 
Would you be opposed to a system that uses 2d10?
Do you think players will have find it difficult to adjust to a new dice system?

I don't think it will be a difficult transition.

I agree with your analysis that it will drive results toward the median.

If that's what you want for the game then go for it.  I'd be leery of such average-biasing in (for instance) a heroic game, but would find it quite workable in a game of (say) office bureaucracy.

What's your game about?

d0 is a popular system, but it's very far from all that's out there. You definitely don't need to use it just because other people do. I don't think it'll be much of a leap for anyone. Also, if you're set on a dice that generates numbers 1-20 and want a bell curve you could go with 3d6 for even more of a bell curve. (Although 2d10 would be fine too).

And also, I agree with TonyLB: What's the game about?

Really the game background and storyline are little more than a line item on a to do list.  We have yet to add many of the details regarding history, religion, kingdoms, ruling classes, nobility etc.  We do have a basic list of religons down etc.....

My group really became disenfranchised with how cookie cutter the standard D&D 3.0, 3.5 & 4.0 systems were.  The rules were clunky and the thing that really put the last nail in the coffin so to speak was the fact that, A. Characters felt like they were steam pressed and baked in a mold made of titanium 2 the spell casters had like a 5 minute work day, they could do an impressive amount of Damage in a short period of time and then they were done. 

So the cookie cutter character classes have been done away with in the system that has been created.  Everything except initial stats are now point buys.  There are no longer cross class skills, yes if you want to create a "cleric/mage/fighter" type of character you can still do that but the system is open ended enough to where your holy warrior type character isnt stuck walking around knowing the three primary skills of a holy warrior, detect evil, lay on hands and smite evil.  In the system we have created he can now do all thoose three things and still be able to bathe himself and hold an intelligent conversation with an innkeeper.

Mages now have renegerating mana, their ability do massive amounts of damage has also been toned down.  Spells are now completely open ended, you the player get to choose, range, area of effect, duration, wether or not you have verbal, somatic or materal costs and how you spend your mana.  There are no real spells there are what we call "seeds" for example..................

The Fire based seed.
Spellcraft check: 18
Mana costs 2 for every d6 of damage. 
Target: Self    1 mana
          Touch: 3 mana
          1-3 hex: 6 mana

It's honestly, designed as a completely open ended gaming system.  Do what you want, when you want, however you want, just so long as you can pay the cost.

My thoughts on the d20 vs. 2d10:

First, let's differentiate a d20-based system against the "D20 system". the D20 system made a bad name for itself during 3.x, but as a player, I'm more than willing to use a d20 in a game. There's no reason that the d20 should be tarnish just because people didn't like products put out by a company that has moved on from their old ideas and now has 4e.

My game "Apocalypse Prevention, Inc." uses a specially-designed system that uses a d20 and I have yet to hear either "OMG, a d20? Really?" or "Good to know you're sticking with the industry standard." Players are approaching the game as a new entity and enjoying it for what it is and not for what die it uses.

Then, I agree with TonyLB and that a middle of the road game is great for using the median-based 2d10 mechanic. But games of extremes benefit from the d20.

Hope that helps!

-Oni

I sincerely doubt your player will have a hard time adapting to a 2d10 system. I´ve been a user of d20 for 6 years but the last 2 i´ve gone to 2d10 and its been a relief. There is nothing more annoying then a combat encounter going awry because of some 20 or 1, the only problem really is that it makes the job harder for you to balance because a few bonuses will tip the scale alot (rolls 11->13 is statistically very different).
I have found bonusses needs to be suppressed slightly more in 2d10 then in d20, so that there is still a risk involved and that not so skilled players still have a chance (this of course might not be so obvious to begin with for players that their +2 skill makes a world of difference, but after a few rolls they get the picture).