I'm an Excel user myself and I'm really impressed with Numbers, its my second favorite application second only to iPhoto.
One way to give Numbers a more Excel feel, simply right click on the menu icon bar and select "Customize" and add the features that you want or use most frequently.
Also the "Inspector" which is the hidden powerhouse of Numbers contains an endless amount bells and whistles, you can get to it by clicking
- View
- Show Inspector
* Your right adding formula's is VERY easy, this is the way Excel should have been.
I especially love the "Scale To Page" feature, I've had alot of problems with resizing Excel spreadsheets in the past!