Well, my second batch of beer (after Mr. Beer) was a prehopped liquid extract with corn sugar added. It was pretty much undrinkable- I had a couple of friends who drank it. You do get some bitterness, but no flavor/aroma hoppiness at all. I think the recipe called for just dumping in in the fermenter and adding water and the called-for sugar. I don't recommend this- instead of sugar, I'd now add dry malt extract. And some hops, too. It was cidery and harsh and just not good at all.
It's just as easy to buy an UNhopped liquid malt, add water and boil and add hops. And it's about 100 times better. We can talk you through whichever you decide on.
Lorena