Personally, developing a website that is high traffic perfomance based, I stay away from database transactions whenever possible. Obviously they are neccessary, so I use an ORM, and page level object variables to minimize the number of server side calls I have to make.
Nested transactions are an awesome way to minimize your calls, I steer in that direction whenever I can as long as they are quick queries that wont cause locking. NHibernate has been a savior in these cases.
