Leather seats are easy to maintain, aren't they (never had any)? For a clean freak it's tempting (choosing removable/washable seat covers I was surprised to find them reviewed by leather owners
), besides that - not at all. In USA it looks like leather or poor man's "sensatec" leatherette (I did not appreciate it in a 3 Series loaner) are all the options, you'd walk for cloth. Australia can be the same.
Regarding lumbar support. I did consider the feature, even went out to try it (in a 7 Series). The opinions were most contradictory: people either loved it or loathed it. One person complained he'd gone for an expensive package solely to get it for his faulty back but ended up appreciating it could be adjusted is if absent (made it even worse for him). I did not find it comfortable and had to skip it utterly out of budget but now that I've improved my posture quite a bit I guess it would do... It's not really expensive so it looks safe/wise to order it just in case if possible.