First, what is your degree in? Perkins loans may be eligible for forgiveness if you are in certain fields, such as medical, education, some areas of law and social work. If you are in any of these fields you need to look into forgiveness before you consolidate or you'll lose the ability.
I work for a consolidation broker and there are indeed many, many companies out there. Part of my job it to deal with other lenders and I'm not crazy about Sallie Mae. All of the largest lenders have the same problem - revolving customer service people. The majority of the time when I call them I have to tell the rep how to find the information I need. Many times they are not even familiar with the industry terms. It happens in any large company in any industry, the customer service personnel are just not trained enough prior to putting them on the floor. Sallie Mae is just as likely to sell your loan as anyone else, all lenders have the capability but few do. Our lender has never sold a student loan, ever. Not to say they never will, but it's not as common as say mortgages which are sold fairly regularly.
When picking a consolidation company you want to make sure you know the overall costs. Any lender should be able to tell you what the total interest you will pay over the life of the loan is. Having that figure will make it much easier to compare different repayment incentives. I'm not going to say my company name because I didn't post this as an ad but our current lender is offering .5% interest rate reduction for an automatic payment from a checking or savings account and 1% reduction after 24 months of ontime payments, which is just about the best in the business currently. Use that as a starting point and see if you can find better. I have seen a few that are offering 1.25% reduction after 48 months, you would have to get a total savings quote to tell if it is a better deal or not. Be careful of offers for cash back up front, they almost always cost you more in the long run by having lesser interest rate reductions. Ask if your repayment incentives are permanent or not, with some companies if you miss a payment you lose your incentive and can't get it back. Some companies make them permanent once you qualify for them. With our comapny you lose it if you miss a payment but you can earn it back again.
My personal opinion as someone who deals with these lenders regularly is stay away from Sallie Mae, EdFinancial, Nelnet and Wells Fargo. I often have to advocate for our clients and these companies have not shown me they are student oriented. YMMV. I'm happy to answer any further questions, one of the other parts of my job is writing educational articles on how the industry works.