Not necessarily, you just have to understand what you're doing. See
Optimizing Microsoft Office Access Applications Linked to SQL Server
http://msdn.microsoft.com/en-us/library/bb188204.aspx. It gives you
the lowdown on how to use Jet efficiently, which is basically the same
rule of thumb as for any client-server application -- fetch only
needed data; don't "link" to the whole megilla. Used correctly, Jet
gives you a lot of flexibility (basically you can use it to cache data
on the client machine, much the same way you'd use a DataSet, except
with a decent query engine and the ability to persist it, if desired).
Stephen Forte and I are co-presenting a session at TechEd this year,
DAT312, "Solve Problems without Spending Money: Access and SQL Server"
in which we'll cover using Access as a front-end to SQL Server data to
solve various business problems when there isn't a need (or there
aren't the resources) to develop a full-fledged .NET app. See
http://www.msteched.com/sessionlist/default.aspx for details.
--Mary