Since some time (2 years or so), I have started using old (mostly brass) lenses increasingly, and I like them more and more. I have used them mostly for 8x10, though. The issue of sharpness is here even less and issue than for 4x5, but I think many old lenses are quite sharp. I do like their softer contrast: I always seem to get details in the shadows, and those a little bit gleaming highlights. Even nocturnes appear to come out very nicely with the lenses I use.
I picked up nearly all of them from ebay, two or three were not what I expected (not the seller's fault, it was just a try and hit from my side). I have an excellent Dallmeyer Stigmatic of about 300mm focal length, lots of movements, screw off the front lens and you get 600mm, still of usable quality. I don't remember exactly what I paid for it, but it was something between 40 and 70 Euro. Then there is an Emil Bush 470mm Aplanat (I think); looks like a stove pipe and works beautifully. Same price range. Had to calibrate the f stops, though - and these lenses need to be stopped down even for focussing. This is less because of a focus shift but because they are just not sharp with the highest f-stop.
The most expensive lens by far I picked up is a ca. 230-250mm Rodenstock wideangle Aplanat, a small brass lens similar to a wide angle protar with a very large image circle, suitable also for larger formats than 8x10. I paid considerably more than 500 Euro for this (including customs tax).
For 4x5, I think there is less choice for good old wide angle lenses; I do have a no-name Aplanat-type lens of about 210-230 mm which works well on my 4x5, giving me also enough movements. And there is a 110 mm protar, supposed to, when stopped down, just cover 8x10 which mine does not, but it is a nice, sharp but uncoated, moderate wide angle with ample movements on a 4x5.