Here's a couple of things I've noticed over the past few days that it may pay to be aware of.
1. DisableEventHandlers property not available on eventhandler containers
I have generally assumed up until recently that eventhandlers do not actually throw events themselves. Theoretically if they did you could enter an infinate loop of eventhandler executions.
Well it turns out my assumption was wrong and eventhandlers actually DO throw events of their own. However, these thrown events are only caught and handled by eventhandlers in a parent package (if one exists).
Why is this important? Well simply that it doesn't make sense for eventhandlers to throw events of their own. Eventhandlers are there to catch events, not do regular processing like in the control-flow which is from where you DO want to capture events. Unfortunately the eventhandler container does not make the DisableEventHandlers property visible so you cannot stop an eventhandler from throwing events and having them handled in a parent package.
Is not a bug as such but its annoying and wold be easily fixed by allowing us to modify DisableEventHandlers property!
The only workaround I have found is to prefix each object in an eventhandler (e.g. with "__") and in the eventhandler in the parent package employ a filter to make sure that events thrown by objects wth this prefix are not actioned.
There's a bit more info here: http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=102957
2. Cannot create identically named variables with differing scope
By rights it should be possible to create identically named variables as long as they are scoped to different containers. And it is, with one caveat - they must be members of the "User" namespace. If you try and create identically named variables in a different namespace the SSIS Designer will complain at you.
This is most definately a bug!
There's a bit more information here: http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=102700