I worried about this when I was purchasing my oscilloscope, as it seems to be given a lot of prominence compared to things like bandwidth and number of channels which I felt were more important. I ended up buying an LeCroy WaveJet which only has an update rate of 3,600 (from the spec sheet - I've not been able to measure it yet), but it does have 350MHz bandwidth and 4 channels and was at a very reduced price as it was 6 years old (though never used - it had been sitting in stock for a long time).
I'd like to gain a better understanding of the practical implications of having a refresh rate of only 3,600 (or 1,000 according to Agilents app note comparing their scope to the WaveJet but I suspect they didn't set the WaveJet to its optimal settings). To a certain extent it is a quantum thing. Unless your update rate is up at the 1,000,000 mark like the Agilent 3000X series the percentage of blind time is still very large so you're going to miss glitches anyway. (If you buy 20 lottery tickets instead of 1 you're more likely to win but it's still very unlikely that you'll do so.)
In Agilents app note on glitches when testing the WaveJet (and others) they set the memory depth to give maximum sample rate which means that a lot of invisible memory points are being stored.
If I was looking for glitches I'd set the memory depth to 500 to match the screen and maximise the update rate - if you see a glitch you then are aware that glitches exist and what trigger condition to set to recapture it at maximum sample rate. So in the app note at 1 microsec a division the WaveJet rate is dropped to 625 but at 1GS/s the number of samples captured per screen is 10,000 i.e. 20 screens worth. Setting it down to 500 might give something like the stated rate of 3600 - still only a tenth of Agilent's but more respectable and about 3.6% of the actual screen rate. With the blind time being 96.4% and events happening say 10 times a second over a period of 5 seconds the chances of missing the event is only about 13% so the WaveJet owner would have an 87% chance of spotting the glitch. The Agilent owner of course would do better with 35,000 or 35% his chance of missing the event is more or less zero.
By the way, your scaled figures for the Rigol probably should be slightly adjusted. At present you have an update rate of ~3 at 50mS where the screen takes half a second to draw and ~6 at 20mS where the screen takes a fifth of a second to draw!