I will offer my two cents then in regards to the O2ptima. I got mine in January of this year and it was my first rebreather and I had never done a try dive either. I chose this one because my dive shop/instructor uses it and I got a smoking deal (5 hour unit for half price). After having slugged around double 120's, putting on my little backpack of a unit was a dream.
My buddies and I dive almost every weekend, so 8 months later I have had plenty of time to get acquainted with it. It is compact, sturdy, easy to assemble and prepare, works every time, and functions very well. I love having the cartridges over the granular sorb - easy in and out. And with the BMCL and BOV, no dangly hoses and switches nor bulky counter lungs hanging around my neck and chest.
In summary, I am not 'meh' about mine, I love it. Easy to care for, easy to use, and a crap ton of capability.