I love the Kupa nail drills....I use a Kupa mani pro myself and find it is very easy to use, it doesnt vibrate as much as other drills do, its affordable, and you can change the drill working speed to suit you, and change the direction of the drill bit etc.
I have used other brand drills before but didnt like them as much as the Kupa!
Im from Australia, and I bought my Mani Pro from the US as it was much cheaper!! In Australia they retail at around $300 - $400 for the mani pro!!
The mani pro has only 15 000 Rpms, so it is most suitable for a beginner or a small business.