Surprisingly no. First of all, if you're familiar with vibrational dampening and compliance, the idea is for it to work within a specific response to the system. So as rubber slowly ages it's going to become less effective anyway. Plus, using the solid mounts stiffens the structure, which in turns transfers the energy to the suspension dampers (shocks), which is more effective at damping that a rubber mount. In other words, let the suspension do it's job. This is why modern vehicles that are unibody do use an isolator and why engineers go to great lengths to stiffen the chassis structures.

So does it make it noticeably harsher? No. I swapped mine with no other changes to the chassis or suspension (same shocks, springs, etc.). Drove it before down the road, across train tracks etc. Swapped them and did it again. No noticeable loss in ride quality. But man did it tighten going around a curve! Most people I've heard say otherwise are usually quoting 3rd-hand, or theory only. Or they changed more than the mounts (double the spring stiffness, bigger sway bar, stiffer shocks, etc.) so of course it's worse, but it was the other changes not the mounts.

If you're concerned about ride quality versus harshness with decent handling:
Run solid mounts, subframe connectors, a big front sway bar, quality adjustable shocks (QA1s, Viking, Koni), and moderate-rate springs.

P.S. If you ever intend to go with subframe connectors, you'll want solids anyway. You do want to have the rear half of the body tied directly to the front frame and then allow the front body structure flex relative to the same subframe.