I have a pair of early 70's vintage Falcon San Remo bikes. Pretty much your top end road bike back then - 531 butted tubing, all Campy NR, Cinelli Giro bars, Clement tubulars on arc-en-ciel or weinmann rims.
Why get them? Sentimental attachment. I rode a San Remo back in college (late 70's/early 80's) in some local club crits, did fairly well. Just wanted to relive some memories. And, they're excellent riding bikes.
Cost? Paid $500 for one in mint condition, $225 for one that had been hanging in a garage for 20 years, and had grime everywhere and a bit of surface rust on the chromed parts. Bought the restoration case because it had a larger frame, more suited to me, my wife gets the smaller one. The distressed example is cleaning up nicely - just needs cables, tires, and those expensive brown brake lever hoods. The old Campy NR gear has held up quite nicely. Still tight and useable after 30 years.
Ride them? You bet - update the rims to modern 700c clincher and you're good to go. The old Reynolds frames ride very smooth, yet they're really not flexy. Interesting to compare these classics to my reasonably contemporary carbon framed Trek. If you take the aero wheels out of the comparison, they aren't much slower, especially on the flats. The downtube shifters are a nuisance after using indexed brake shifters, but otherwise the contemporary bike doesn't represent that much of an improvement. The fit and finish on the old bikes is so much better than what you see today. Chromed Campy fork ends - sure don't see that any more.
Plus, one looks so stylish on a classic racer.