I use Perfect Effects, which comes with Perfect Layers built in. You don't have to only use the inbuilt presets as it gives you a way of processing your photos in a similar way to, say, Lightroom, but adding one effect per layer. For example, you might add a Tone Enhancer layer to fix any problems with exposure, then a Color Enhancer layer to bring out or tone down the colours. You might want to add a Photo Filter - an 80A Cooling Filter, for example, add more Blur to a particular area, or turn your photo into a Duotone image, all with the ability to mask the effect to particular areas of the image.
The built-in effects are: Black & White, Blur, Borders, Color Enhancer, Duotone, Glow, Photo Filter, Sharpening, Texturizer, Tone Enhancer, and Vignette. All are fully adjustable. For example, the Tone Enhancer has sliders for Brightness, Contrast, Blacks, Shadows, Highlights, Local Contrast, and Clarity, and has a checkbox for Auto Contrast, and a Photoshop-like Levels grid for making changes to individual Red, Green, and Blue channels or the Composite of all three. The other effects have similarly detailed settings.
When you finish making your changes, PE flattens all of those effects onto the original picture layer and returns them as a single image (e.g. in Lightroom), or a single layer (e.g. in Perfect Layers, Elements, or Photoshop CS).
Once you've stacked up a number of effects on an image you can, if you want, save them as a preset. It's a great way of building your own 'look'. Or, if you're like most photographers, your own 'looks'.
I own all of the Topaz plugins and don't use them anywhere near as much as I use Perfect Effects for simple photo processing. But for some pictures, ReMask is a great tool. OnOne's Perfect Mask looks, from the example videos available, to be easier to use than ReMask, and the results look OK at normal zoom levels; they don't often show the photo zoomed in to 100% so I can't say how accurate Perfect Mask is.
Replacing skies is one of the situations both ReMask and Perfect Mask are usually demonstrated in videos as the results for both are impressive once you know how to use them. Since any of the single OnOne plugins comes with Perfect Layers for free, it doesn't matter if you own the entire suite if you just want to do one job. To replace a sky from within Lightroom, you take the photo into Perfect Layers and add your sky image there. You then take the photo into Perfect Mask and define your mask to cut out the bits where the sky should show through. And, from what I've seen in the videos and webinars, the sky layer is also taken into Perfect Mask and will show through as you define your mask. This makes sky replacement pretty easy as what you see is what you get.
You probably already know that Topaz ReMask doesn't work with Lightroom and needs an intermediary program such as Elements to do the actual layer work. But since every OnOne plugin comes with Perfect Layers built in, any of them make a good way of 'adding layers to Lightroom' though, of course, you can only use layers in PL, not in LR itself.
There are a number of videos on Perfect Mask on the OnOne site, and I seem to recall that some of them mention Lightroom.
http://www.ononesoftware.com/learn/training/video/category/perfect-mask-5-2/
