I've always used the Visual Studio products, but I elected to work with the beta 1 version of Visual Web Developer 2005 instead. It's a good product, but clearly in an early beta version.
Many people reported that the VWD beta 1 expired on 1 March, but my copy is still working fine (don't set your clock to the future...it apparently breaks VWD beta 1).
There are going to be many changes from VWD beta 1 to beta 2. You certainly can load up the beta 1, but understand in advance that many features will change when the beta 2 comes out (they're saying late Q1, but my guess would be April-May).
You might want to consider EXPLORING the beta 1 version, but don't get too into any details around the datasource concepts, as many of the names and implementation details will be changing.
I've had no problems running VS2003/.NET 1.1 and VWD2005 beta1 side by side (I've not been actively using SQL Server 2005 yet, only the SQL 2K desktop).
Just my two cents...enjoy! There are many wonderful new features in ASP.NET 2.0!