I chose to pay before someone removed all my downloaded content... Have to get it all back up on my PC again (still got 2 months left).
For "regualar" members, it is very slow, and a lot of the stuff on there comes in big files and needs multiple downloads. I tried downloading one train (a class 156) just as a trial and was given an 8 hour estimate. In reality, you need the premium membership. The £20 for the year is a good investment if you're going to use the resource, and trust me there's some good material on the site.
If you're a bit unsure, the £3 for one month may be enough to let you try a couple of the routes out and see if you want to make the bigger commitment. But I can assure you that, if you want more content for MSTS, it is a very good website and worth every penny.