I've taken the Flex 6500 into three contests, CQWW CW, ARRL DX CW, and ARRL DX SSB. I am pleased to report that it functioned very well as a contest radio in both SSB and CW modes. My contest software is WriteLog, and the 6500 worked very well with the search and pounce feature of Writelog, sometimes resulting in 4 contacts per minute in a target rich environment.
I've been licensed since 1959 and started contesting in the mid-60s. I've had many high-end radios throughout the years (Drake C-line, FT-1000D, TS-950SDX, Icom 775, Signal One CX7, Orion II, FT-1000 Mk V Field, KX-3, FTdx-5000), so I'm accustomed to state of the amateur radio art performance over my 55 years of amateur radio. In my world, the two aspects of an amateur transceiver that define contest performance are selectivity and user-interface. Based upon these 3 contests I recently worked, I place the Flex 6500 at the top of the list. Prior to the Flex 6500, I had been contesting with the FTdx-5000, a very fine contest radio. But I had to embellish the FTdx-5000 with an LP-Pan unit, sound-card, and PowerSDR-IF software to have panadapter capability. Although a nice solution, this combination was subject to overload and various other sound-card difficulties that sometimes brought contesting to an end. In fairness, I did have one screen-freeze using the 6500 in these three contests, which had to be resolved by a reboot. So I am not saying that the 6500 can not be improved upon, but it did perform extremely well in these 3 contests and helped me claim personal best scores in 2 of the 3 events.
Contesting with the Flex is a visual, as well as an auditory experience. You don't have to laboriously search for QSOs with your ears...because you can see where they are, and you can see where they "ain't". Using the high resolution panadapter is like shooting fish in a barrel, especially on a sparsley populated band. Ever since I was first introduced to a high resolution panadapter on the Flex-1000/PowerSDR, I have felt blind on any radio without it. Yes, there are pretenders in the panadapter arena, but put them side by side with the 6500 panadapter and you will understand why all others are pretenders and not contenders.
The selectivity of the 6500 filters, CW and SSB, are better than anything I have seen in amateur radio. I've spent a small fortune on IF crystal filters over the years. I have been sacrificed upon the altar of the "filter shape factor" god all too many times. The shape factor of these digital filters, both CW and SSB, are excellent. I won't use the phrase "brick wall" because I know they are not 1:1 shape factors, but they are very, very close to 1:1, the best being about 1.04:1. The best of the analog filters I've ever measured was 1.4:1, which looks like a sieve compared to a 1.04:1 digital filter. The worst shape factor of these digital filters is better than the best of the analog crystal filters.
The 6500 solved a issue with previous Flex series transceivers...CW latency. Simply put, I can not detect any CW latency in the 6500 series (nor can I detect any SSB latency). Plug in the key, set the side-tone, turn on iambic, and have at it. Or if you have a favorite external keyer, turn off iambic, and send away.
Another issue I hear being tossed back and forth is the knob vs. mouse argument. There is a solution for the knob guys (like me). I use the Flex Control encoder for precise tuning and for RIT/XIT tuning. I am confident that more knob solutions will be coming in the future. I use the Flex Control encoder a lot, and it sits right by my CW key, so it is closer to my hand than a VFO knob would be on a big box radio (which translates to less time to effect a VFO or RIT/XIT tuning adjustment).
Another nice contesting feature is to be able to monitor activity on 3 other bands with the other panadapters. No changing bands and spinning the tuning knob to approximate how much activity is on the band. Just look at the panadapter activity and decide if you want to change bands or not.
Although transmit SSB audio fidelity is not a contesting issue, I must add that the SSB transmit audio is very nice on the 6500.
As capable as it is today, I consider the Flex 6500 to be in it's "teenage" years considering the future capability that can be programmed into it. Yes, it takes time to get the software level highly refined. Yes, there will be software glitches that require another revision. Yes, your personal pet feature may be a long time in coming. But find someone who has a 6500 or 6700, and spend an hour with it on a crowded band...I think you will be impressed. I know I was.