UCLA's Teaching Assistant union has done excellent work for the TAs. The union has negotiated significant improvements in benefits (prior to organizing there was no dental or optical coverage, for example) and in protections (TAs can now seek mediation if they are being asked to work longer than 20/hours a week, etc.). The union has also negotiated pay increases, but the pay increases have been largely (but not entirely) swallowed by increased union dues. Still, getting additional benefits without a loss in pay is a good deal.