Here are my thoughts after going from many years SQL Server to an extended project in Oracle:

I certainly found a lot of things in Oracle quite 'alien' to me and was initially very resistant and cynical.(particularly having to use a third party tool to develop - TOAD which I think has a user interface like a car accident).

The poster who mentioned that Oracle has loads of baggage is really on the money. MS can now sit back and emulate all the good parts of Oracle without having to take on the baggage!

I'm impressed with Oracle packages as they almost seem like classes to me

-Variables which 'reflect' existing table meta data

-Custom data types

-Multiple 'methods' within the package all returning different types

So you can truly wrap up a large piece of logic in a package which has various methods which can be called.

The other thing that impresses me is the optimiser and the way it can decompose multiple levels of views. You can define many layers of views to contain your business logic and usually be happy that it will still perform. Back in SQL 2000 I tried doing this and it appeared to be effectively materialising the data at each level rather than doing any smart 'rewriting' - maybe things have changed by SQL 2008 though.

In summary, you'd be well served to jump the hurdle and get some experience to make an informed judgement about the two different platforms.

PS at a current client we indeed have what seems to be a political decision to move from Oracle to SQL Server.