I would like to respond to a lot of the negative criticism from other reviewers: first, VM's documentation is good. VM's forum section also has an extensive collection of posts. VM is not a good solution if you do not like to read or you do not know how to search for solutions to potential problems.
VM has an extensive amount of options and will take some time to customize and get just right. A lot of the negative reviews seem to think this is a problem; however for me this is one of the most useful things about it. It makes the extension very flexible and able to accomplish more than a lot of others.
I would not recommend the extension for someone who is lazy or who doesn't want to write (or learn to write) some PHP. That is what keeps me from giving this extension 5 stars. If you are going to build a large site, you will likely have to tweak it just a bit in order to get it to work just right. You can find a lot of great workarounds in the VM forums, and I recommend that if you tweak VM that you share your solutions with the VM community.
For people who are comfortable with PHP and CSS, this is a 5 star extension, for less experienced developers or people who are short on time I would say it is a 4.
The Web Application Firewall is the killer feature of this extension - the e-mail alerts that you can set up for security threats are invaluable. The ability to give the administrator login page a special location (like /administrator?impossible_to_guess1989) is also an important feature. It also contains a number of tools for stuff you should already be doing even if you don't have the extension, such as changing the db prefix and password protecting the admin directory.
AdminTools Pro was relatively easy to set up, and the documentation is extensive.
Pros: Quickmode is extemely easy to use, you can rapidly develop and copy forms. Lots of options when setting up forms. Large selection of attractive themes. Ajax validation is great. All submissions can be logged to the database for review.
Cons: I had an issue while I was a subscriber - the form's rollover colors setting can cause problems with select lists when enabled. It was a very simple fix, just to disable the rollover colors. (I should note that I raised a support ticket about this issue and Crosstec helped me identify what the problem was - their support is very responsive.)