As far as I know, you can't consolidate your private loans with your fed loans. If a company is saying that you can, i would be hesitant to do business with them. I would advice you to choice a company that is well know and has been around a long time. Worst case scenario, if you go with a small company and they fold, your loans will be sold. All borrower benefits promised by that company run the risk of being lost if your loans are sold. I chose to go with Sallie Mae which is the larget loan consolidation player around. Chances are my loans will not get sold, and I don't foresee them folding in the near future. I also looked into graduate lending who look like they have a good offer (probably the best around. I was just concerned that they have no track record yet and since they are a middleman it is one more step of processing. I don't want risk losing the benefits of consolidation before July 1, as the rates are up about 2-2.5%.
Good Luck