Glad to be of help.

Hex (which is sold by Daz) has displacement painting....although I have the programme when it was being sold on special offer for $2 by Daz, my graphics card didn't really take to it and there were occasional crashes.

What I use is Silo, it only models (I import and render in Bryce) and it's a honey to use. Very simple and very powerful and intuitive at about $100. Yes it's not cheap, but it's nowhere near as expensive as the industry leaders like Maya and Zbrush etc. I would recommend Silo. The version which has displacement painting (Silo 2) is still in beta, but I find it works very well and it's a steal at the price. You will also get the 'stable' version Silo 1.4 which doesn't have displacement painting, but if you want to get into modelling, I would start with this. go to www.nevercenter.com

Hope this helps but if you need any more just post another message.

Here is a screenshot in silo with a simple terrain in progress. Don't be fooled though, it's not that easy to make a complex terrain using a 3d modeller alone - it will take some practice. Much better to make a rough of your terrain in silo and then use photoshop to put in roads and rivers and Bryce to smooth it and add noise.
Cheers

Ravs