>You can install SQL Developer side-by-side with Express

You can, but why?

>
>>Don't want to mess up my current installation - I'm not a big fan of installing/re-installing stuff.
>>
>>I do want to switch to Developer's version of SQL Server 2008 instead of Express I have now, though - because Express doesn't have BI and when I do import tasks I can not save packages. Also I can not fully play with SSRS using Express.