The clause indicates that "except as otherwise provided" in the sev agreeement, I waive any right to or expectation of entitlement, payment or benefit incidental to or associated with emplyment, term or seperation by or from the cmpany, including, but not limited to, severance compensation.
Anytime someone is fired or subject to a Reduction In Force, the employer wishes to protect itself from potential state or federal law suits arising under statutes protecting against discrimination and/or pay and benefits. A severance letter is usually given the employee to sign that waives the employee's right to sue the employer for any and all matters known and not known to the employee.
As these letters are signed under duress, unless the employee has elected to retire, some courts will uphold them regardless of the circumstances, and some courts will declare the contract to have been signed under duress, and therefore void them if a suit is later brought.
I cannot advise you as to how TX courts view these agreements. I do note that it is never good to burn one's bridges behind you for you may need a recommendation in the future, and a prospective employer, if you are not retiring, may find that you sued a prior employer (all law suits are open to public inspection - some final judgments are sealed) and refuse to hire you for other reasons, but in reality out of fear you may turn around and sue the new employer. It is a small world.