As I mentioned in a recent post, I was disappointed by a disconnect between the address book and caller ID handling of some Uniden phones I purchased. If phone was programmable, someone could fix this without waiting for the vendor to release a new phone.
Such phones would also have a community of people working on them so details about exactly how they work (like how the caller ID ignores address book entries) would be relatively easy (vs. nigh impossible) to find out pre-purchase on the internet.