Can answer only from experience with the 150mm which I've used for almost 4 years now. Its a good lens. The image you take occupies only a small part of the finder frame (unless you buy the auxilliary) and this can make focussing a little tricky to start but you'd get used to it. Naturally as you get longer the fact that you can't see dof ttl gets more important. But the lens quality and look of the photographs it produces is very good.
The 210mm is a different proposition though and doesn't tempt me at all. Its not rangefinder coupled, I believe, so not only can't you see dof but you rely on distance assessment to focus the thing. No thanks.