I use PSP 7 all the time for textures and postwork, and for digtal photo manipulation as well. It's not possible to paint on a 3D model directly as with the 3D paint programs, and okay, maybe you can't do everything that you can with the more expensive 2D image apps, but for the money PSP is superb. I prefer the interface to Photoshop as well (although that could be because I use it far more often). If you save renders as TIFF files to get the alpha channel information, Poser leaves 'blank' any of the (grey, unless you changed the colour) background still showing. If you've filled in all your background with props and scenery then you won't have any blank bits in the alpha channel. I sometimes render twice- once with the scenery, and once without the scenery and with just the model, so I've got the alpha channel info for the model. Load up the with-scenery render as the background layer and the no-scenery render as the next layer. Then 'load from alpha channel' in the Mask menu from the no-scenery version of the render, to seperate the model cleanly from the background layer.

Couple it with UVmapper to create texture templates. If you save working documents as PSP native format to keep your layers, you can save copies in JPG format and run Poser at the same time with that JPG loaded as the texture. Poser will pick up any updates you make to the texture and you can see what the changes look like.