what are the main problems with the clarity?
For me, lack of USB as mentioned already - the AV80R charges off the USB port which I find really handy.
Also, I usually use 1:250 charts rather than 1:500 as I find them cluttered, so I have the same problem on the Clarity (and I'm not paying 130 quid for the 1:250 on top!). I found the zoom to be ok, there are 9 levels I believe, but not as sharp as the AV80R, and I'd rather have the GPS style view where I can choose what shows and what doesn't at each zoom level rather than see the actual chart. Zooming in on the clutter just shows you more clutter, and zooming out doesn't remove info like the AV80R can obviously as it's a chart.
The AV80R has terrain topo on the map colour coded by height which I also liked, not to mention it doubles as a car sat-nav which the Clarity doesn't. Lastly, the CAA chart updates are more expensive than the database updates for the AV80R.