We have added new features to MP since 1.0 and in particular the recent MP 1.21
I retract my statement, as I stand corrected.
My perception of MP not being a well supported product stems from the fact that there are features that are either not working well or are not implemented which have annoyed me, such as extended mouse behavior, like the tilt wheel on my Microsoft mouse. Sometimes the third/fourth buttons don't work. Part of the problem is people's perception. The software industry seems to release a new major version with plenty of new features every year and relative to this perception, Multiplicity seems rather stagnant.
I would love drag and drop copying of files. The cut/paste is nice when it works (which is most of the time, but the times it doesn't...it's frustrating). I've had copy/paste issues with files as well as the clipboard (moreso the clipboard). If I copy files (Ctrl-C) on one machine, then cross to the second machine, but never paste, I have to wait while the files get copied to the second machine's temp folder.
And since you asked, it would be great if you could drag windows across to other machines. I know that is getting away from its primary purpose, but when you get so used to accessing multiple machines across multiple monitors, it would be an extremely handy feature.

But, my biggest issue is connectivity. I posted on this in a different thread, and don't want to go into it in this thread since it's really off topic. But, the only solution provided was to try the latest beta (and it helped, but hasn't solved the issue). One feature I would really like is to let me choose which network adapter (or subnet) the server and client uses. I run Hamachi on all of my machines and MP has a hard time figuring out how to connect (and it usually ends up that they don't connect). MP always seems to bind to the Hamachi connection and there's no way to change that. I end up having to turn off MP on my client to get a pretty stable connection.
I am hopeful development time can be found in the next couple of months for this.
As we all are...

Thank you for the prompt response. I love MP and it is an essential tool that I rely on on a daily basis both at home and at work. For the most part, it works very well, but that is a double edged sword, because the times that it doesn't can really be extra frustrating. I can't imagine computing without it. I just wish it had the user base like WindowBlinds so that development on MP will get the priority it deserves. How many major versions has WindowBlinds gone through since Multiplicity was released?