Snack is absolutely right about the new batterydoor.
Some people like the 415X with the extended battery, simply because its better to hold (+the extended power of course). Others say it looks like a pregnant ipaq (guess its what you can expect if you leave a 4150 with a 1940 in the dark at night. Maybee its the rumored 6XXX baby thats in there :lol: )
Personally i like the battery, and would recomend it.
Have a look here for pictures and further discussion:
http://discussion.brighthand.com/sho...threadid=99665