Two years ago I wrote some comments about OmniPlan. In two years, OmniPlan has certainly gone through various improvements. A quick guesstimate is that they've been mostly fixes, and eventually 1.5 did bring some new features:
http://www.omnigroup.com/applications/omniplan/releasenotes/
I have a lot of respect for AMBERV, and highly recommend reading her comments below. To me they make more sense than comments such as "OmniPlan is the best PM solution for Mac" or "This program is a friggin masterpiece."
Fortunately for Omni, there are people who will pay $150 for OmniPlan. I would not be surprised if version 2 comes out in 2009 with a new price and an upgrade fee for current users. I'm pretty sure that version 2 is going to be a huge improvement over version 1, which is the one I'm rating (1.6.1).
My overall impressions of OmniPlan have not changed. For simple projects OmniPlan may be more than sufficient. Having said this, I've never chosen OmniPlan for any of my projects. It's evident that Omni's strength resides in superb visual design and ease of use, but for this first version Omni lacked the focus of a true Project Management company. Merlin 2 and FastTrack Schedule show a different level of maturity in that regard. (These are 2 programs that I've used more frequently, but there are at least a dozen other Project Management programs for the Mac.)
It's nice to see a pretty interface, but for my needs that's not enough. Compared to other "Project Management" software I have, I would choose OmniPlan over Jumsoft's Operation, but in 2 years I have not chosen it over Merlin 2 or FastTrack Schedule.
These 2 programs are more expensive than OmniPlan, and to me they've been worth it.
My Omni licenses include:
OmniWeb
OmniGraffle Pro
OmniOutliner Pro
OmniPlan
OmniFocus
Out of these, now I only use OmniGraffle Pro (4) from time to time and have no plans of upgrading their software anymore.
To their credit, Omni has some amazing people offering customer support.
Like AMBERV, "I used to recommend them [OMNI] to everyone...Lately, I never recommend, and I haven't bought a license in years."