It's not about getting rid of Microsoft: it's about getting rid of Oracle. Their licensing costs even for a very large shop may start out cheap (think 90% discounts) but will creep up over time. And when you inevitably manage to get a combination of oracle-dependent data, queries, processes, etc entrenched the prices start to climb and the even more expensive options come out. Oh you need more performance? Go horizontal with RAC. You need to go faster but can't reengineer things? Exadata will fix you right up.