FYI: If you buy the second batch, you're not really going to break even IF butterfly labs ships before / around the same time. Now, if Butterfly Labs never shipped or shipped in June or so, then the difficulty from soley Avalon ASICs would be still profitable
If they ship, if the specs are what they hope and what else is hashing on the network. asicMiner are out there also.
Each hw round Avalon go through gives them an opportunity to bring down costs and improve on their design - so in the same time frame there's a chance for the units themselves to improve.
Now they have shipped - they're the only real baseline we have.