I had an Optima MK3 and really really liked it. I ended up selling it, however, because I couldn't get used to not having the 6th digit. On receive it doesn't really matter since you can tune to the other station. Calling CQ, however, it's a deal breaker, for me any way. When you call CQ on an open frequency, you just don't know exactly where you are. With the unlocked clarifier, you can guess about where "center slot" is, but you are likely to be off at least 100Hz, often more.
It's not a terrible tragedy to be off 100-200Hz when calling CQ, but it makes it a bit easier for answering stations if you are close to a round frequency, say 28.425.00 rather than 28.425.20 or 28.424.80. For me, it comes down to good operating practice. It's just sloppy practice to not know where exactly you are transmitting.
The earlier Optima versions had a detent at center slot which would be very helpful for staying within 50Hz or so of where your VFO reads. Alternatively, there should be an RIT on/off switch so that you can lock the clarifier and be sure that your transmit was exactly the same as your receive frequency. Ideally, there'd be a 6th digit AND a clarifier on/off button. Especially for a radio as good as the Optima which has excellent frequency stability, it's a glaring shortcoming not to have the capability for better frequency control.
According to Dave at Yeticom, he is mindful of this shortcoming and hopes to include a 6th digit and/or a clarifier on/off in future versions. Once he does that, I will be first in line to buy the new version.