We have one of these prams with a 2.5 YO and a 4 MO.

When we are out walking with both, we find it a bit of an effort to keep this thing straight - perhaps it's just us...but we do find that we are constantly changing the direction to keep it straight (even with the wheel in swing mode)
You can switch rapidly between swing mode and fixed mode using the knob behind the front wheel (I know, you know this already). When in swing mode, the single front wheel will tend to follow the direction of the prevailing camber.

I'll run that by you again in English: most paths and roads are laid with either a single slope away to one side for drainage, or (more usually) a higher centre and lower at both sides - the camber. A buggy with a solo front wheel that swivels will naturally tend to follow any slope that it is on.

This is particularly nasty when walking across a slope!

Our Quinny (fixed front wheel) will not do this, and frankly seems to weight less, but it's old and needs constant attention. The e3 looks great! Swings and roundabouts.

Rich.x