SQL Server Express edition has some limitations, one of them is a 4 GB per database limit.  If you are thinking there should be no problem since your data will only be one or two GBs, you might be setting yourself up for a fall.

True, you can have a very large database (4 GB is large too many people), but you have to watch out for the details.  Different operations may require temporary storage inside your database, which can cause you to hit the limit while your database is far from the 4 GB maximum.  

Recently, I was working with a test database to evaluate the overhead of using Full Text catalogs with SQL Express 2005.  The test database was 1.4 GB of mostly text consisting of over 280,000 rows.  I was checking out if there was any effect by adding another column (simple varchar(50) nullable column with no data) and it failed to change the table due to exceeding the 4 GB limit.  Hmm?  Yep, it shot the database size on disk to move the 4GB for a 1.4 GB actual size.

My experience was simply a test and there was no hardship to me, but if this happened to a solution I deployed for a client and the database was not able to be modified, it could be a major problem and cost at least the cost of SQL Server 2005 Workgroup version to fix.  There might be some setting but I have yet to find that can help this issue.

At least now, I know in the future I will have to keep those possible extra costs in mind when dealing databases that exceed the 1 GB mark if the solution calls for SQL Server Express.