In my limited experience, the vegetable rennet tablets are OK for fresh cheeses, and I made my first very tasty Camemberts with it. If you are going to make longer ripening cheeses vegetable rennet can impart an unpleasant flavor.
I have had some troubles with vegetable rennet, at least at the quantities Riki Carroll recommends. (guessing the OP bought her Mozz. kit) I had a couple of makes with flocculation times in the five minute range. From what I gather reading here, we want to match set and acidification times for most cheeses. Camembert is a bit less sensitive because the flavor is really developed by the action of the mould. (so says the Wiki recipe)
As a general rule, recipes here call for about half the rennet and culture that Rikki uses. I've got several makes aging since discovering this, so I cannot yet tell you what a difference it will make. I'm still settling in on my quantities of culture and rennet. It's a lot easier to adjust the amount of liquid rennet than the discrete steps of tablets.
Another hint from a newbie who just discovered the difference quality milk can make. I've had decent results using store bought milk, but last weekend I went to the farmers market and bought some local creamline milk. Not only did it yield about 25% more curd, those curds tasted like cheese after a bit of draining. I could have filled more than 5 Camembert molds. The dairyman mentioned his P/H milk was available in the supermarket, but I missed it. At a $.20 premium over the standard stuff, I used it to make a Stilton approximation Sunday. Probably didn't need it, but I substituted a pint of cream for the same amount of milk and drank the remainder. Comparing the taste of that milk to Grocery store standard was like comparing a craft brewed stout to a low calorie light beer. I'm going to "splurge" and use it for every day consumption. Can't wait to get some fresh milk from a dairy I discovered 10 miles from home.
Hope this helps.