Questions about new consumer API

Hi guys,

I'm interested in the new Consumer API.
http://people.apache.org/~nehanarkhede/kafka-0.9-consumer-javadoc/doc/

I have couple of question.
1. In this doc it says kafka consumer will automatically do load balance.
Is it based on throughtput or same as what we have now balance the
cardinality among all consumers in same ConsumerGroup? In a real case
different partitions could have different peak time.
2. In the API, threre is subscribe(partition...) method saying not using
group management, does it mean the group.id property will be discarded and
developer has full control of distributing partitions to consumers?
3. Is new API compatible with old broker?
4. Will simple consumer api and high-level consumer api still be supported?

Thanks!

Best,
Siyuan