I loved it when I had it - so much I paid for the subscription so I could do "fancier things" with it.
BUT!!!!! They did not tell me that the subscription one was not mac compatible. I could only change assignments at home (we're a Mac school) on my PC. This did not always work, because I would get busy, etc. They assured me that it would be mac compatible very shortly. this summer they stopped responding to my e-mails and phone calls, so I did not renew it.
But I agree with Barb in that it is very easy to use. And the free site is mac compatible.