The problem with any alternative miniature though is 'scale' while manufacturers do state what scale particular models fit (28mm in the case of WHFB) they do not always match up, much like how Size 11 US and UK shoes are different sizes. Consequently, I have always been reluctant to purchase alternative miniatures not willing to risk ending up with figures that cannot fit into my existing collection.
However, Bugmans Brewery - the primary forum for Dwarf players - has a great thread in which it reviews a large number of alternative suppliers. Reviews that include brief notes on scale issues. In the same part of the forum is a post which offers a great comparison of Mantic vs. GW Dwarfs (click here), probably the best comparison I have seen.
Size comparison BfSP GW Dwarf vs. Mantic Games Dwarf
If I had found this comparison last year I would have seriously considered purchasing a large number of Mantic's miniatures as the price advantages are quite large. But, as I now have all of the figures I need Ill have to put it down as a missed opportunity. However, there is nothing stopping any other Dwarf player out there giving them a go.