Lots of denominations, Catholics, Calvinists, Lutherans, Baptists.. etc. etc.

[John G.]

Are there any groups, churches, theological positions that form a definite obstacle to salvation?

Yes. Those that do not rely on salvation by grace but add all sorts of "requirements" are basically subtracting from the finished work of Jesus on the cross.
In Galatians, Paul warns that anyone who does so has fallen from grace and is obligated to adhere to the entire Law (as if that's even possible).

 

[timothyu]

I've yet to see a bride that doesn't prepare for the wedding.

 

[Neogaia777]

Are all of these saved? Does it matter which denomination or sect you belong to...?

How much leeway is there when it comes to personal preference, or are there denominations that are wrong?

Are all the main ones that we find on this site basically ok?

There will be many individuals who are decieved that will still be saved.

All the sheep that are really sheep will still be saved, etc.

God Bless.