Yes they're good. More races have been won with DT shifters than any other type of mechanism. Just none in the last 10 years.
I've ridden DT since the late 80's until this spring when I bought a new Kona with a 105 10sp group. I love STI/brifters. Shifting while turning and out of the saddle is great. That being said I rode my old Specialized w/ 7sp DT yesterday over 60km. I had to think a little more about gear selection and no matter how hard I pushed my break levers I couldn't get my derailleur to shift (coincidently this is now considered a benefit of the new DA 7950 electric shifting).
As a secondary bike DT's are fine. They last nearly forever. At least mine are going on 17 years. Easy maintenance. I looked at the STI's when I needed a cable replaced and threw the bike in the back of the car and took it to the shop.
If it is a classy bike with a good group I'd say rock on. You'll get lotsa bang for the buck and when you watch 'Quicksilver', 'Breaking Away', and TdF pre-90s you'll know what they're doing with their hands.