Also, I've found that with a sequential box (sadev box in a clio), gearbox oil changes are needed more frequently, as the selector can sometimes get clogged with fine silt like matter (i.e. oil and worn gearbox 'swarf'). As Peter C has said, the change does need to be very firm to ensure engagement. Although you can go straight down the box without using the clutch, I find a slight 'dip 'n' blip' helps takes some strain off the driveline.
It does give massively improved acceleration, esp if flat shifting is possible. Great fun to drive as well.
As per Danny's comment, I don't think it detracts from the driving experience, but personally, it allows me to drive harder, as I'm not worried about possibly mis-shifting (as per a few hairy moments at the Ring in my SLR!) 😬