.....not me but several people I know have bought stuff from Forgeworld. The quality of the modeling is obviously exceptional. You can see that in the pictures.
The casting quality hits about 99%. In other words every resin model maker in the world gets a bubble or two once in awhile but FW's castings are probably the best in the biz.
One drawback is ordering from the UK. Normally not a problem but FW does their casting in batches so if your order gets there while they have some on the self you'll get it pretty quick. If they're out... you'll wait... and wait... But when you do get your kit if a piece is messed up they (Games Workshop in general) are really good about replacing that part without having to return the whole kit. Email them first.
Here’s a US based retailer who keeps FW stuff but you have to know what you want when you go there. They don’t advertise it. And they are redoing their FW right now anyway.
thewarstore.com
The price is high but "worth it?" is relative. The overall quality is awesome and nobody else puts out stuff like this so there's nothing to compare too. It depends on how bad you want it.
That's all I know.