The observation I have is that the link mentions the same old things that Connie Edwards said when he was interviewed by the press ... that the flaps caused a large nose-down tendency. We had a former Luftwaffe pilot give a talk on the Bf 109 and he was asked about Connie's comments. His answer was eloquent.
He said that obviously Connie had not been taught to fly by the Luftwaffe! The flap wheel is right next to and the same size as the stabilizer trim wheel. They are separated by about 1 inch or so. In Luftwaffe training they were taught to move both wheels together and there was no trim change when that technique was used!
I also know some 5 - 6 pilots who have flown Bf 109s / Ha.1112s. All of them say the slats operate easily and cause no problem except for occasional symmetric deployment when you get to slat speed while the ball is not centered. The asymmetric deployment will not cause a flight control issue, but could cause an issue if you were actively shooting at a target because it caused momentary yaw until both slats were either in or out. That being said, the slats were both firmly out when in the landing pattern anywhere near touchdown speed, and retracted well before typical combat speed was reached. The Bf 109 was most comfortable in the 180 - 280 mph IAS range. Much faster and the Bf 109s stick forces became heavy, with the ailerons becoming heavy above above 310 mph and the elevators being almost immovable at higher speeds. The slats extend about 150 mph in normal flight, slightly higher if maneuvering.
So, according to German pilots, it was very good in typical combat situations and not at all difficult in landing configuration unless the pilot was inattentive combined with gusty crosswinds and a runway with a lot of traction, such as dirt. On a grass strip, it is said to be pleasant to takeoff and land. Unfortunately, the few Bf 109s flown today use pavement which exaggerates any bad tendencies. The aircraft might have a much better general modern reputation if they could be operated from grass, which was the wartime normal surface. If you watch the Bf 109s takeoff and landing runs on grass, such as at some UK airshows, you see nothing out of the ordinary. They do tend to look a bit snaky on pavement.
There is a lot of hogwash about the Bf 109 suffering some 30% or more takeoff and landing accidents, but little to no proof of that. If you look through German records (at least the ones I found some years back that were translated into English), I found nothing unusual about the takeoff / landing accident rates. It might be sobering to go look through the takeoff and landing accident rates in US pilot training. We were under no wartime stress there and were never under attack, but we had a lot of training accidents in initial fighter conversion training. It probably has more to do with transitioning from a trainer to a fighter with the quantum leap in power available than with the landing gear geometry. Shoving the power all the way in at low speed to effect a go-around has WAY different consequences in a P-40 or P-51 than it does in an AT-6. I'd bet the same can be said of transitioning from an Arado trainer to a Bf 109 or from a Chipmonk to a Spitfire.