I think you'll be fine if you just add a little flexibility into your application for handling the building of the connection string.

for example, what should happen if i wanted to install your application on my machine, for example?

I have two SQL server installations,A default 2008R2 and an instance named .\SQL2005

you don't want to force them to install another instance of SQL Express if they already have SQL, right?

or what if they have a SQL server on another, dedicated SQL machine and want to use that, instead of a local SQL Express instance?

you'd need to add a little somthing to your application to buidl the connectionstring based on those changes.

some crappy fake code as an example:, where i assume a couple of text fields were added to it.

string myDBlocation = @"

Data Source={0};

Initial Catalog={1};

Integrated Security=True";

//Connect Timeout=30;User Instance=True";

myDBlocation = string.Format(this.txtServerName.Text, this.txtDatabaseName.Text);