No such thing as semi HDR, Photomatix, is the best. I think they have a free trial, if you are any sort of student, I think you get half off. And you must use a minimum of 3 exposures.
regardless of software, it also involves lots of practice and work to create great HDR images; it is not a one click operation, this includes exposures as well.
there is photomatrix, Nik HDR Efex Pro. HDR Expose, FDR, to name a few and I believe CS5 has upgraded this feature , however, i haven't tested it out and can't verify it's usefulness