I don't have an Xtracycle, but I have a tandem and often ride it by myself. Same issue, only even more so.
I find the stokerless tandem as easy to ride as the single bike except in a few situations:
– Steep downhills need to be taken with more care, especially if the road is bumpy. There is very little weight on the rear wheel, so don't brake too hard while you jump a bump or the rear wheel will skid! That,s especially important if the road is likely to be slippery, because at that time, one should favour the rear brake.
– Climbs in the snow. Actually, that's a welcome challenge. My pedal stroke has become much more even because of that. Call that a year-round benefit.