@TJ,
thanks for posting that. The community has done a great work on that.
@Gwu,
I will list a couple of important changes.
1. Testing of current component:- do not use $bp->current_component=='something'
instead use bp_is_current_component('something')
2. You will need to assign a wordpress page to each and every component which needs a top level page(in older term a directory page). Like for your contact plugin, you will need to assign it a top page.
If you are using older code, you will need to have the component slug same as component id in order to allow bp to help you create those pages.
3. hook order:- There are some changes in bp_loaded, bp_init and some other hooks, so there are chances that a plugin will break if it hooking to wp action forcaching screen with higher priority(like 1,2 etc)
4. Other than that, there are some minor changes but won't affect most. Like you should not use the older constants like BP_ACTIVITY_SLUG instead use bp_get_activity_slug()(has a function for each of the older constants).
Since I have updated all the premium plugins from BuddyDev for the current BP Trunk, I found two issues nagging. 1. The loading order of hooks(I am planning to write a detailed tutorial on that) and another managing the directory page(I had too many issues while making BP branded login compatible as It uses 3 top level pages).
Also, the problems will depend on the plugin and how they were written, if Bp skeleton component was used as a model, there are chances nothing (except the directory page assignment) should break for your existing setup. They may break on newer installs when you will be using the hierarchical page structure for the community like site.com/community/members style(look we have got community as the top level page which is parent of all the social pages).