I am assuming you are considering big tele’s or very wide angles. The ‘normal’ zooms or focal lengths are not worth loosing the metering and auto focus. You will have to carry a separate exposure meter. Unless you are getting a terrific deal, like free on the old lenses I feel it is not really worth it. Plus it seems that folks selling old lenses price them quite high given their age. Granted if they are in focus and work, no problem but new is not that much more….and you get the auto functions.
You may find a better deal finding someone who is selling a newer camera and a bunch of lenses together. Hey you can never have just one camera! 😉
.
