I've mentioned this elsewhere before, but I've had experiences at both ends of the H1B chain.
In one workplace & location in the US: The H1B workers were...not very good. Adequate, and hard working, but not highly skilled and they were brought in mainly because the location didn't want to/couldn't pay wages good enough to hire skilled US-based talent. There the H1B workers were (in general) fearful and unwilling to complain, because they knew their personal odds of getting another US gig were NOT guaranteed. This left me understanding the various H1B complaints, as the workplace was terrible.
In another workplace in a different US location, the H1B workers were equal or better than any US-citizens working there. The workers were highly sought after and were interested in speaking up to make the workplace better. Switching jobs for them WAS a hassle, but a very doable hassle, so the workplace had keep them as happy as non-H1B workers. This left me understanding the OTHER side of the H1B issues, as these workers raised up rather than lowered their workplaces.
I've had multiple friends spend months uncertain if their visas would be renewed (Most companies seem to employ offshore lawyers to handle the visas on the other ends, and I've heard some horror stories about those lawyers sometimes vanishing, or misfiling). Also, I've had friends that had to stay put in a job during a certain phase of getting their green cards - a change in job title would reportedly move them back to the end of the queue of that step. (No idea about the specifics)
All in all, I've found it pretty hard to generalize about H1B workers and the process as an entire whole.