There's a major disadvantage to doing that. If you use a query hint you are forcing the optimiser to pick a plan using that index, even if another index would be much more optimal for the query.
Unless you are really, 100% sure that you know better than the query optimiser what index is most optimal for the query, don't use an index hint.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability