I don't think anyone would disrespect the Leclerc, but in most of the discussions I've read/had, there were concerns over its light weight, comparatively limited protection, low amount of ready ammunition, (22 rounds immediately accessable to the auto-loader before you have to refill that.) and its auto-loader. (a design decision that noone but the Russians have ever thought was a good idea)
Its certainly quick, but not substantially quicker than the other MBT's. Its arguably the most maneuverable MBT out there, but the quick surge of acceleration given by the Abrams' gas turbine potentially puts it a close second. While those things are ENORMOUS gas guzzlers, their simplicity, relative silence, and power-to-weight ratio is some of the best in the game. The types of armor in use on these things are always semi-secret, but I've heard it suggested that their version is inferior to the latest Chobham armor, although that's probably impossible to confirm.
And I've read about a dozen competing claims on accuracy, rate of fire and the speeds at which they can do it. I've also heard the merits of its fire control/target acquisition systems. I think both the Challenger and the Abrams use a Canadian version. Haven't been able to find competent information on which is better.
Its gun is slightly shorter than the German/British varieties. Abrams are of course are the shortest around, but make up for it by using DU rounds.
I don't think there's anything approaching a consensus on the MBT thing, but there seems to be a slight plurality out there rating the latest Leopard as the best, followed by the Abrams, with alot of competing claims out there on the Challenger 2, Leclerc, and even the Merkava (though I'd disagree with its placement amongst the elite MBT's, too specialized).
Than again, that trend can mean nothing. Since most of the people commenting have never been inside a tank and are basing their information on a ton of googling. (like me

)
(Flame mod on : does F22 has been proved ? nor F35 ? nor Leopard 2A6 ? Flame mod off).
The difference is of course that not a single 5th generation fighter has been seriously tested in combat. While multiple modern generation MBT's have. (but not the Leclerc)
All of those aforementioned tanks are quality designs that in the hands of a better trained crew, have a good chance of fairing well against any of the others.
To conclude: you are right. This tank can be seen as an "unproven" one. Maybe it's because France isn't as prone to go to war as USA (for example).... Maybe... But this is another problem.
How can you hope to win any military hardware pissing contests if you don't stomp on some defenseless third world nations every few years? (j/k of course)