Go for it. My friends got their H1s from consulting companies like the ones u mentioned and their papers were ready within few weeks as they did the premium proocessing.Both of them paid the company's fees as demanded by them,after few months of waiting and trying in their own they were offered nice jobs as well, as transferring you h1 is much easier than finding a job that sponsores you. It will be a good move for you as your opt expires in june, it is 100% legal and they meet the DHS requirements for employment and visa regulations, Indians are the best in such crookery and they do it so perfectly in a way the rocket science works. Have no second thoughts and go for it.