I've stayed away from the 28-70/4 due to the reports of its problems.
The F35-70/3.5-4.5 Macro I have was $39 in EXCELLENT condition from
KEH, and has proven to be a very good performer for such an
inexpensive lens. Good sharpness and contrast, even wide open but
particularly 1 stop down, and very nice rendering qualities.
Some examples:
http://homepage.mac.com/ramarren/photo/PAW5/23p.htm
http://homepage.mac.com/ramarren/photo/PAW5/33.htm
http://homepage.mac.com/ramarren/photo/PAW5/40q.htm
It's also a small, light lens. Great on the DS for when you want
normal to a little more reach flexibility.
Godfrey