Must not switch to it immediately: Preferences -> Interface -> Check Open tabs in background
Make it open in last tab: Preferences -> Interface -> Uncheck Open tabs next to current
Pick and choose what panels you want: Right check the main panel: You can check/uncheck certain panels. To customise what buttons etc are on the navigation bar. Enable the toolbar editor extension.
Spellcheck: Webkit problem, not Midori. It is fixed if you are using the latest versions of Webkit. If so, Preferences -> Behaviour ->Enable Spell Checking -> Type your language code
Scroll wheel changes tab: It works here.
I've been a heavy advocate of Midori since the days when it was reallly beta. It's come a long way. I actually use it as my main now, firefox installed mainly as a backup..