I would suspect that Adobe left out some well established features so that they could allow people to download and play with the new features.
Including everything (clone stamp, rotate, crop, etc.) would have meant that they were giving away their product for free.
To be useful standalone though, some of that functionality has to be offered. I've been thinking about this; I need to update my Mac's OS before I can run Lightroom, but IMHO to be able to print from it without an excursion through Photoshop, I will need:
1. to be able to rotate and crop
2. to be able to retouch at least minimally
(My point&shoot has a hot green pixel, my DSLR gets dust, ...)
3. [ strongly preferred ] be able to dodge & burn
I'd currently draw the line at layers: once layers are needed or wanted, then it seems to me (until I change my mind!) to be Photoshop territory.
I agree that the wishlist will be as long as a piece of string. One way to minimise the pain for all concerned would be to offer very keen discounts for buying Lightbox and Photoshop: that way people who only need one or the other can buy them, but people who want both don't get perturbed about paying for functionality twice over.
I don't know that functionality will have been deliberately left out of the beta to protect Photoshp revenue in the short term: I can see the attraction of protecting Photoshop sales, but that would limit the usefulness of user feedback and I'd expect very price sensitive users to prefer a bundled copy of Photoshop Elements to buying the full version of Photoshop anyway.
[ Edited to correct product name. ]