I was just told not to use
READ UNCOMMITTED also called dirty read in SQL 2008. A new possibilty exists:
READ COMMITTED SNAPSHOT
The problem with the first one is that if conn A reads a large bit, conn B do update, conn A reaches the updated bit and reads that, conn B rolls back, then conn A got illegal data.
If using the snapshot read, then conn A reads only on a snapshot as long as conn B is doing update. This snapshot contains the before transaction data.
This makes sence because had connection B just been a little later, then it would have been the same situation as with the snapshot option.
Thanks to Jesper Johansen