It depends on what you want.
Mandrake, like XandrOS or lindows is for people who just want a non-windows desktop for reading emails, listening to music, or typing. If thats what you want, then yes, mandrake is #1.
If you want to 'make computing fun' like it used to be, Mandrake will not allow you to do that. It acts like a safety pen... leaving you in a nice soft, safe environment. Superior to windows, but not up to snuff with what you *can* have.
You can still install all of the applications you want, but you're missing out on a whole bunch of features. (Her majesty: the command line.)
I started out with Mandrake, and wiped it off of my hard drive a month later in favour of slackware. What I ended up with a lot more power... losing the ease of use that came with mandrake.
So like I said, it all depends on what you want. If you change your mind, slackware, bsd, debian (for masochists only) or GENTOO is but a few clicks away. Since you already downloaded the ISO's, I say stick with mandrake for now.
One more thing...if you like mandrake,
join the club. Its only a few bucks, you get access to tonnes of great things (including support), and it'll help the developers.
Here are some fun links:
www.distrowatch.com
www.kde-look.org
www.linuxquestions.org
http://slashdot.org