Nebraska and Florida are certainly contestable. There is a good chance that the senator West Virginians pick to replace Byrd will be a Republican, but that might not happen in 2006.
Let's hope Byrd does NOT retire. WV is only just starting to tilt to the GOP. If Byrd goes this year, there will be few good GOP candidates to replace him, and the Demonrats will probably lock a newcomer in place, like they did in AR and LA. If he waits six more years, there will probably WVn Republicans with the credibility, exposure and clout to take the seat.