Got on Minifigure Speedway yesterday, and I'd say that it is a good addition to the park. As a coaster I think I do prefer it to the Vekoma models; it had a bit more force and because the end of the first half is a life and not a spike you actually take the backwards section at a good pace.
It was getting between 800-850pph yesterday when we rode it, which was pretty good. It meant that the queue from the entrance to sitting down on the train was about 25 minutes, despite being advertised at 50 minutes. They do not have enough queue line for the ride, but I am going to say that's a good thing!
Now the theming and landscaping. Well let's be honest, it is dire. Legoland is a really well presented park with nice landscaping and decent, if not at times a bit cheap looking, theming. The huge minifigure is nice, but other than that the way they have presented this new ride is so so poor and at complete odds to the rest of the park. You have a temporary looking fence outside the ride, most of the ride area is just dirt with weeds growing in it, lots of exposed steel and in the queue line the vinyl stickers are already being peeled off by guests. I'm hopeful they will make improvements, but it would have been nice if they had opened it looking somewhat presentable.