I have the 42" Hydraulic tiller on my gx345 now and like the fact that it tills the entire path as you move forward. That was the one thing I didn't like about the 30" tiller. Other than that it was great. I also like that it can till in both directions by flipping the brackets around. Not easy, but at least it can be done.
Sergeant and I both feel we did well by the sale since he really wanted a Mechanical tiller and I wanted to move into the Hydraulic tiller. The hydraulic tiller is a beast, but you have to have the stamina to handle installing and removing since it is very heavy and awkward or have a helper which is almost impossible, since nobody ever has time to help.
I always try to have 2-3 suitcase weights on the front with the 42" hydraulic tiller because it can be difficult to turn. Going straight is fine though.