To be completely honest here.
For me its primarily a looks/polish thing, i like ubuntu alot but i just hated its overall look and feel, mint on the other hand is much more pleasing to the eye and i love the mintmenu and the artwork. hence the "from freedom came elegance"
Aside from just looks i also like the preinstalled apps that it includes alot more, so i dont have to install as many new programs when i upgrade, tho there are a few that i do prefer to install (exaile, azureus, skype, k3b, vlc).
and as JTAL604622 and 67GTA said, the community here is really good and if you suggest an improvement theres a chance it will change. You can help change mint for the better.
mintinstall: I'd like to say i use mintinstall to do it but ususally i dont because i like to get the very latest versions of programs so i find i go to the website itself to get them bypassing synaptic aswell. But its pretty much same versions as synaptic so if i were to choose id use it over synaptic.
mintupdate: i use this all the time a great safe way to install updates.
mintupload: I've never really found a use for it yet since it only uploads for 2 days, perhaps if you could add image uploading services like imageshack to it and then upload pics using it then i would use it...
mintdesktop: Nice simple app, quite useful.
mintwifi: Havent used yet.
But what you see has happened in such a small time frame just over a year and its already climbed the ranks to be one of the best desktops, so i can imagine that as it grows its just going to get better and better.
The wiki on linux mint has some more info http://en.wikipedia.org/wiki/Linux_Mint
and a review on distrowatch has some more info http://distrowatch.com/weekly.php?issue=20071126#review