Everything I've seen says that their numbers are not so good.
Think Progress Reports:
The Texas Privatization Plan:: Sen. Barbara Boxer (D-CA) took the president up on the "Texas idea" suggestion. The senato's office has released a report looking at the 1981 Texas plan. In 1981, three Texas counties "decided to opt out of Social Security and instead to provide their public employees with a system of privatized accounts." The analysis done by Boxer's office and the nonpartisan Congressional Research Service "compares two sets of families in three different income brackets [and] shows what happens to their retirement in 2005 under Social Security and under the Texas plan." The conclusion: "By examining the actual system in place in Texas, this study shows that Americans are worse off with privatized accounts - not in theory, but in reality."