I have used version 1.5 for storm drain hydraulic analysis, but not for the hydrology.  Simple program, and seems to work fine.  I have used Los Angeles County software also for storm drain and channel analysis.  It has it's limitations - such as single barrel pipes only - but very powerful.  Advantages of Stormcad are the windows interface, graphic and customized tabular output.  We generally use HEC1 for hydrology or spreadsheets for rational method analysis; HEC2 or HECRAS for channel analysis; HY8 or culvert-master for culverts.  

For hydrology, you may also want to try SMADA. Low cost and has many options.

http://www.cee.ucf.edu/classes/cwr6535/PROJECTS/spring96/

interesting comparison of SMADA and SWMMM (for continuous simulation)

I had been using the Haested Stormcad program since the mid 90's and recently upgraded to their newest version. Many of the feature changes were welcome and I find the program much more efficient than it was.

I agree with cvg about StormCAD's user interfase. I am using the AutoCAD version myself and it is great to be able to work in this powerful drafting environment.

My StormCAD version is 4.0 and the multiple barrel feature is already implemented in this version. I believe the newest versions (4.5?) have lots of new improvments in the profiling capabilities.

Hydrocad. http://www.hydrocad.net/
Intuitive, flexible, inexpensive.
Does not integrate with Acad, but the newest version can place a bitmap behind the diagrams. I've used it for years and think it's perfect for my needs. Download a demo copy and give it a try.

TCEbob