Gary - Lehman is NOT the best keeper in the world. He is an excellent shot stopper, one of the best, but he's certainly not the best keeper out there. He's the weak link in the Arsenal defence, and I sincerely hope Arsenal don't manage to change their keeper because with a better keeper they'd be much harder to beat. Lehman makes far to many mistakes, is not commanding enough in the air, and has a penchant for hitting opposition players with his clearances - in fact, he reminds me of Calamity James (though not as bad!)
Better keepers in the EPL? Peter Cech comes to mind, he's been outstanding. Niemi & Cudicini were also better last season - but then they had more to do. I'll not go down the normal route and stay Kirkland, because he seems to be made of glass. I'd say Kahn is a better keeper (and I don't like him), much more commanding.
At the end of the day, Lehman has never lost an EPL match - but that's playing behind the best team in the Premiership. He's certainly contrived more than his fair shares of draws with his "impetuous nature" (as Sky put it).