The multiple choice part is not difficult at all--common sense for the most part, but then again I've been driving here for over 2 years (thank you, renewable student-visa driving privileges). I got 100% on that part.
The second part of the theory test is a hazard perception exam, which consists of 14 video clips. You have to click the mouse every time you see a road hazard developing. I got 53 points of a possible 75 on this part. The passing mark is 44 points, so I passed with a good margin but I was nowhere near perfect.
Like Ginger, I bought some practice software for both the theory and hazard tests. It is very useful, and also like Ginger, I did not see a question on the multiple-choice that I had not seen before in practice sessions. I would NOT have passed my hazard test without the practice software. I found the hazard test to be a bit biased against experienced drivers--the software package also warns about this--the "feel" of real driving actually works against you a little bit, and I found myself failing the practice sessions over and over until I stopped treating it as real driving and started treating it as a very expensive video game.
I need a few lessons to get rid of my Americanisms (hand-over-hand turning; coasting to a stop; signaling first--to show intent to move--before checking mirrors, apparently that is a BIG no-no here). I also need to practice reversing around a corner, a maneuver that I believe is illegal in New Jersey where I initially took my road test 22 years ago.
Since I have a bit of leisure time and some money to travel, I'm hoping to be able to go to Wales for the test, where wait times are far shorter than here in the London area, and do a 3 day intensive training just beforehand. I need to try to set this all up today as I'm off to Berlin this evening (my sweetie is in another opera there). But if that plan doesn't work out, I'll just book a test for 18 weeks hence and call them every farking morning until I get a decent date. No way am I giving up driving just because of their bloody queues.