I played a little bit in it. It was buggy, and crashed commands constantly. I don't think i had a solid install. When I got the rep on the phone he got it working through webex.
1. it's vertical in a friendly familiar interface...autocad.
2. Most of the elements lacking in revit can be done in DM.
3. Easy to learn.
1. exporting to a BIM enviroment doesn't produce data driven elements only solids.
2. Trying to coordinate with other trades in revit. you have to export a Arch model from revit and import into cad enviroment.
3. Performance of machines in 3D rich (sold, polyface) enviroment.
4. Autde$k is a monopoly and revit will be "the" program.
You may disagree, but you can only deside for yourself. Play with it, you may like it.
"It's hardware that makes a machine fast. It's software that makes a fast machine slow."
Design Master support is top notch. If you find a bug in the software, the developers will send you a fix within a few days, usually within a few hours. They are also very responsive to feature requests.
I can't dump on Revit MEP too much since I've only used it a handful of times, but I did not find it intuitive or very customizable. I spent a lot of time waiting for objects to move, views to change, and files to save. I also like being able to use LISP and VBA to quickly write routines for repetitive tasks. I believe the only way to manipulate Revit is through the .NET APIs, which aren't all that easy to pickup and run with. (Did MEP get the VSTO? IDE yet?)
Once you get a feel for how DM works, the workflow is intuitive and fast. If you've written LISP or VBA to use with AutoCAD, most likely these routines will work with DM. The database they use is not locked, so you can create your own custom software to query DM items in the database. (undocumented feature... proceed at your own risk..)
The software used to crash a lot, but the later releases are pretty stable.
If your client wants a MEP Revit model, Design Master is probably not the way to go, but if you're deliverables are just the plotsheets, I think Design Master is going to save you a lot of time.
I use both Revit 2009 and Design Master. I like using DM a lot more than Revit because of speed and customization. It's a straight forward process in DM. What I do is do everything in DM and then link the DM drawing to a Revit view, and then when a view needs updating, just update it in Revit. The only drawback, which I'm trying to figure out now, is the plines in AutoCad, which make up the homerun arrows, come in as one width.