Remember that accounting rules were recently changed.  So we don't know if they are showing a profit because of a genuine turnaround, or if they are showing a profit because they are calculating things differently.  Specifically:

The Financial Accounting Standards Board said Thursday it changed its guidelines for so-called mark-to-market accounting. The new guidelines will require companies to value assets at prices based on what they would be sold for in an "orderly" sale as opposed to a distressed sale. The new guidelines will kick in for the second quarter and not be reflected in first-quarter results due in the coming weeks.

 So, what's happened is that all the bad assets on their books can now be marked as more valuable than they were before.  Furthermore, the banks were doing a lot to write down losses last year to get as much of that out of the way as possible and make later performance look better.

This all wreaks of smoke and mirrors to me and while it's a boon to investors in Goldman Sachs I don't believe this is evidence of a turnaround.  The economic fundamentals still suck and there's still tons of bad debt and inflated asset prices in the system.