For 2-3 people teams, a DNN install serving as *master copy* will do just fine. Especially if you use MSN to syncronize efforts (ie don't have two people working at the same ascx at the same time). And automate making backups of the site. The goal should be to have a working master copy at the end of each workday. Scores highpoints for being intuitive

I'd recommend SVN for larger teams, but there is no locking mechanism to lock files and you still need to syncronize efforts. so you could as well stick with the mastercopy/MSN scheme. It does sound more profesional. But it's just more work to achieve the same ( central store for source code without losing it)

sourcecontrol software that do have locking mechanisms are not good to work with, because you need a manager to oversee who does what at wich time. By the time you canh afford a full time manager to oversee all development, you probable have +10 developers. My advise, don't use source control with a file locking mechanism. This is even more work to achieve even less. you can't checkout 2 developers for the same file

I like source safe.  It is what I use in house.  I learned source code control by using it years ago as my first experience with source control.  If you do not need multiple people to work in a single file at the same time then it works well once you start to think like it does.  That seems to be true with most source control systems.  You need to think their way.  If you need to have multiple people editing the same file at the same time then it doesn't do as well.  I have also used StarTeam after source safe it seemed very confusing until I learned its way of thinking (checking out meant something different).  For me source safe makes sense.  You get a copy of all the files you need.  They are read only at that point.  When you need to edit one, you check it out.  That locks it so others cannot check it out.  When it is checked out to you it is read write for you.  When your changes are done you check it back in and it is then unlocked so others can check it out for editing.  The limitation is that one person at a time can edit a file.  You can see who has it checked out, so you can ask them when they will be finished.  The biggest problems are with people who check out a file and then go on vacation.  The admin has to go in and either check the file in for that person or mark the file as not checked out any longer and the person who had it checked out is left to try to put their code back into a revised file when they get back.  It has features to help by showing the difference between what you have on you local machine and what is checked in to help. 

SVN, which I use for one of my customers, doesn't lock files the same and seemed less intuitive to me (source safe guy).  It has features to merge my changes with the changes of others.  That works fine until you both actually edit the same line of code.  I always felt a little uncomfortable with that. CVS was similar as I remember. 

That is my 2 cents