I think Matilda was expected to be a bigger success than it ultimately was based on the superlative reviews coming out of the London production. It had a respectable run but was not the blockbuster that many thought it would be. The biggest complaint was that it was very hard to understand, which I experienced when I saw the tour (and there are reviews from papers across the country that noted the intelligibility problems, so it was a matter of sound design and not the acoustics of any particular theater).
I saw the original Secret Garden tour and was taken by the score & production design and of course had listened to the CD several times over the years. I saw the production in DC that is mentioned in the Playbill article below (the production that originated in Seattle and also played Houston with an eye towards Broadway). It was fine overall (the tree in the garden was breathtaking), but the score really stuck out as being "of an era" to me: that being the era of sung-through musicals in the vein of Les Mis and Miss Saigon and a host of other shows from the same time period. It felt very derivative of that style. Kids in the audience were antsy, for the reasons already noted elsewhere in the thread. I wanted to like it more than I ended up liking it and that was because of the material (not the production).