Any engine monitor is better than no engine monitor. In August 2011, I added an JPI EDM 830 to my Mooney Missile and have been very pleased with it. The information is AMAZING and now when I fly airplanes without an engine monitor, I admit my mind starts playing tricks on me even though I flew for over 500 hours in my former F model without one.
If I had to do it again, I'd probably put the same 830 in there. However, I'm not sure which model it is but one is STCed to replace all your other gauges so if any of you other instrumentation fails, you won't have to repair it or even better, remove it and clean up your panel. The 730 is simply a different display but gives much of the same information. I love the RPM and Manifold Pressure display on my 830 as well as the fact that you can mount it horizontally or vertically depending on what makes sense to you. It is a very clean install and really looks nice as well.
If I were closer to TN I'd let you test it out first hand. I'll be down that way in May, and if you are anywhere near the Mid-Atlantic, let me know and you can see one first hand. I'm sure someone near you may have one to let you view it. Also, see if JPI will give you the Oshkosh discount. They did that for me even though the dicount had ended a few weeks prior.
Take care,
-Seth