From a product perspective you'll find new features in the next few releases that will help you solve this problem. Here goes

1) Today you can use assignment and workflow rules to automatically forward leads and custom objects. We know this isn't possible with the other objects today but if you're using leads it works today

2) Our next release is coming out in the early October timeframe. At that point we're introducing a couple of enhancements that should help

a) Using list view criteria customers can mass share records (e.g. opps, accts, leads etc) to connections. We've also introduced the ability to share related records (e.g. Accounts with opptys, contacts, orders) - so you can mass share both parent and child records at one go - this should help you scale your sharing with the 100 connections

b) We've introduced the concept of 'auto-accept of child records'. So in the scenario where a customer shares accounts and related oppty's, contacts, orders - once the target org accepts the parent account the child records are automatically inserted and related to the right parent in the target org (similar to how Activity sharing works today)

3) In upcoming releases we'll introduce the following key features (not exhaustive)

a) Ability to automatically accept the parent record (soon)

b) Ability to share the same record with multiple connections (soon)

c) Integrate S2S within our sharing architecture so that records get forwarded automatically (this is probably a mid next year feature since it's quite complex)

d) open forwarding, accepting, stop-sharing in the external api so customers can build their own custom rules (mid next year)