I still think using Lightroom presets across the board on a bunch of really promising landscape or other potentially great pictures is, in the final analysis, a waste of time. Invariably you will find yourslf leaving LR and going into PS to finesse the presets you already applied - thus renedering your original presetting work a waste of effort.
You will want to do selections and all the really precise work LR yet cannot do. You will be preoccupied with sharpening. You may need to use a lassoo tool or a quick selection here and there. You may want to selectively lighten or darken part of an image, sharpen up another bit, use adjustment layers and all the multiplicity of things LR can't really help you with at this level of processing. It's not that any of these techniques is particularly sophisticated or difficult to do in themselves - it's just that they're not available in Lightroom and that's why round-tripping into PS is such a waste of time.
LR's TAT tool, the nearest to a selection tool, is good at what it sets out to do, but it's too crude and unselective in my opinion for very fine work. Darken down the blue of a sky, for instance, and watch carefully what happens globally in the picture. In defence of LR, however, I like the way it handles B/W generally and there are some good things here.
I've spent most of my time working in LR from day one dealing with big amounts of pictures taken in places, as far apart as Bali and Barcelona recently. One included a family wedding. Applying across the board adjustments to huge amounts of work in LR was a breeze - fast, convenient and very efficient, especially for the wedding or for those pics which I didn't feel demanded the full resources of PS. But you can do this in Camera Raw too - using the same tools and you won't be in and out of LR+PS like a demented headless chicken. But in the end, I still had to visit PS for sharpening.
However, for the really good stuff - pictures taken out in the countryside on in the city streets which were my humble best attempt at capturing the real spirit of these places, I found I needed PS to do the best job I was capable of - Bridge, RAW and CS3 were needed. Rather than running these selected pictures through LR first and then exporting them to PS, I went straight into PS and remained there, including for printing.
Actually, in the process, I rediscovered the joys of being able to do tasks quickly in Photoshop which would take longer in LR - simply because of having to leave the programme to access what PS has to offer and then returning to LR for whatever other reason. As an experiment, I revisited some pics I had taken in New York before LR came on the scene. I imported the NY 'keepers' into Lightroom and worked on them as if new, but I still found I simply had to round-trip to CS3 for things like Edit-Transform to straighten converging verticles, just as one example. And so on and so on for other things - nothing major in themselves, but not available in LR and critical to the work. The more I continued, the more I realised how much I had missed the comfort of working exclusively in PS for serious stuff.
All of this proved one thing to me which has been bugging me since the first days of Lightroom: if you want very fast, efficient, across the board processing of huge numbers of pictures which can take synchronised processing in their stride and not suffer, then LR is IT and is a brilliant concept with vast potential. For that kind of work, I happily use it
But for the real deal, the freedom to process your best shots to the fullest potential you are able to extract (only limited by your own technical expertise or knowledge which in my case is no great shakes by the average standards on this site!) than Photoshop+Raw is your the only choice. Sooner or later, no matter how hard to try to avoid it, you will end up in PS and be glad that the tools you cannot get in LR are there in PS.
The proof of the pudding came this month when I had to prepare a number of landscape pictures for an upcoming exhibition in a local gallery early in the new year. I can say with hand on heart that for this exercise, I never visited Lightroom once.