I've got two Trumper's soaps: Lime and Rose. The quality of lather is good, but I would say they require a little more work than others (and as Garry points out, I should make clear that I live in London where the water is VERY hard). However, once I've worked it, the lather is good, perfect consistency and doesn't dry out too quickly.
If I were to compare it to my other products, I'd say it needs more work, adding a few drops of water every so often, mixing, adding, mixing, adding, but once you get there the lather is great quality (better than D.R.Harris, for exampl, IMO).
So it might require a little more work, but the result is great. For this reason, I've found that Trumpers soap works best when melted into a wide-lipped lather mug and mixed in situ. Once I get a good lather worked up, I swirl the mug, pick up the lather, and park the brush in the scuttle and I find I don't have to re-load after that.