WASHINGTON ( TheStreet ) -- If Wall Street had become a high-flying Las Vegas casino -- as several lawmakers recently put it -- it's about to become a little old lady buying lottery tickets.

It took more than 20 hours of wrangling after many more weeks of bickering, but finreg finally passed around 6 a.m. ET on Friday. Some of the harshest elements against big banks were watered down just enough to get a coalition of Wall Street-friendly representatives from New York to pledge their support.

But, overall, the Restoring American Financial Stability Act of 2010 is much harder on big banks than anyone had suspected at the start.

In a note sent to clients just a couple of hours after the bill was finalized, FBR analysts sounded cautiously optimistic. They said finreg was "tougher than hoped for, but not as bad as it looks," but made it clear that the game has changed for banks and for anyone attempting to value their stocks.

"Although the conference committee avoided adopting the worst-case scenario, the impact of this legislation remains difficult to quantify," the analysts wrote.

They expect "short-term relief" for financial stocks, now that the uncertainty of what would be in or out of finreg was removed. However, they remained "cautious" about longer-term implications on stock prices.

Among the more surprising wins for the anti-Wall Street crowd was passage of the Volcker rule . Named after former Fed chief Paul Volcker, the provision will effectively reinstate the Glass-Steagall Act enacted after the Great Depression -- something that seemed unthinkable just a few months ago.

The provision will disallow big banks from proprietary trading, or making bets with deposits and other liquid assets for their own profit. As a concession, banks will be allowed to own small stakes in hedge funds and private equity shops, since they can't make such investments on their own.

Another controversial measure regarding derivatives went through as well. The new rule, authored by Sen. Blanche Lincoln , will force banks to house riskier derivatives trading in new, freshly capitalized entities, or simply spin them off.

As a result, there will be no more trading of commodity derivatives or the highly complex vehicles that nearly brought down the financial system at any of the top Wall Street firms. This should have a huge impact on the five big banks that handle 97% of derivatives trading in the United States: JPM ), C ), BAC ), GS ) and MS ).