Hi craftychris, I've had my Robo Lite for just over 2years now and have managed to cut lots of designs using it. It does depend on what kind of card you're trying to use, as the Robo doesn't like card that is too fibrous.
I mostly use Conqueror concept card with mine and always get a good clean cut.
There's new software for the Robo which is free, called Silhouette studio and also a new blade/holder hopefully with the combination of both of these you may get your Robo to cut a bit quicker and better.
The best way to test the card you're trying to cut is to do a test cut first before cutting out the whole design and wasting card.
With mine I used to always use the pink cap with full speed and thickness set at 33, which is a bit naughty but it always cut the card,

but please don't use these setting for paper.

Hope this helps a little, just shout out if you need more help, as there's a few of us with these machines on here.