Short Answer: Yes, but as with all non-compete provisions, proceed with caution and draft wisely.
In a recent decision, the U.S. District Court for the Western District of Pennsylvania considered whether an employee who had left his former position of employment to join a competitor and forewent full severance benefits was able to establish an implied employment contract with his new employer, who had terminated him after only three months of employment despite having given him assurances of future employment. Morini v. Civil Castle Cheese, No. 10-1739, 2013 U.S. Dist. LEXIS 139032 (W.D. Pa. Sept. 27, 2013). The court resolved this issue in the negative.