I hate the skills thing. In OB you won't use some traditional med-surg skills like NG tube insertions or play with chest tubes much. That said, we do use a lot of skills that are different like fetal heart monitoring, vag exams, use lots of IVs, epidurals, catheters, many nurses also learn to scrub for the OR, etc. Assessments become focused no matter what specialty you go into. A med surg nurse could never come onto my unit and function, any more than I could go on hers and function so I figure we're equal
As for variety, well that's a load of hooey. I am working at a large hospital with a high risk labor and delivery department. On an average set of shifts, I may look after a 13 year old in premature labor, a drug addict who hasn't had any prenatal care, a highly educated woman with a pre-existing spinal cord injury and a woman giving birth to triplets! Med-surg instructors tend to forget that sick people still have babies, so you will care for a variety of patients with chronic illnesses like lupus, chron's, diabetes, etc. Even "normal" birth units have a lot of variety because low risk becomes high risk very fast, so you'll see vaginal deliveries, forceps, c-sections, hemorrhages, diabetics, PIH, etc.
I hope you have an excellent experience if you do take the job. I would definitely do it if I were you. Even if it turns out you hate the area, then at least you'll know what you don't want to do after grad