I had my Transmission changed under warranty at about 40k miles (late 2004 E83). No hard 'failure' as such but had some symptoms such as 'rattling bag of spanners' noises and slow selection of reverse when cold, and also some very harsh upshifts under acceleration. The issue of holding gears on incline was initially improved by software update, but it still seems to shift down far to quickly even at motorway speeds when it hits a slight hill.

Anyhow, I really had to fight to get the tranny changed under warranty - they were very reluctant to progress with BMW UK even with a copy of a SIB about some of the problems. New tranny and much improved shifting (you can barely feel it has shifted) and none of the noises/slow reverse selection/slam shifts although the 'hill climb' program in the box still isn't right and I find I have to select M5 when I'm on the motorway to stop it shifting at the slightest incline