Trius
Waiting on Maitani
The score on the 28-48 and the 35-70/2.8 is correct. Beware, though ... the 35-70/2.8 is definitely not cheap on the used market. Other Zuiko zooms can be quite good, but not in the territory of those two or primes. I have not used the 75-150, so can't comment, but what I've read/seen tells me it is very good, though not stellar.
I have a Tokina 70-150/f4 zoom in OM mount that I bought through Cambridge ages ago. It was a "special" production, I've never been able to find anything written about it. It is very sharp and was a steal for the price. But, I don't use it often as I'm generally reaching for primes.
The other Zuiko zoom you might look at is the 35-70/3.5~4.5. Zuiko (and some 3rd party OM mount) lens tests are here,with the usual disclaimer about numbers not telling the whole story.
I have a Tokina 70-150/f4 zoom in OM mount that I bought through Cambridge ages ago. It was a "special" production, I've never been able to find anything written about it. It is very sharp and was a steal for the price. But, I don't use it often as I'm generally reaching for primes.
The other Zuiko zoom you might look at is the 35-70/3.5~4.5. Zuiko (and some 3rd party OM mount) lens tests are here,with the usual disclaimer about numbers not telling the whole story.