No, they suck. The material doesn't last putting an expensive watch at-risk, and gathers dust.
I've been using my third party milanese band since October, it is still perfectly working and doesn't show any scratches or signs of age.
The original one is better? Sure it is, but costs 10 time more. Even if I needed to change my band twice a year it would take 5 years to break even. In a month I'll switch to my knockoff nike band for the summer, not great but good enough and I paid 20% the original cost. I could buy 5 bands with 5 different colours for the same price and never get bored about my bands.
The only original accessory I buy from Apple is the silicon case for my iPhone. It is great and like you said it is protecting a very expensive appliance. My iPhone costs more than 3 times a Watch and it is more likely to fall on the floor so it needs a good protection. I'd buy original Apple bands only if I owned an edition watch, the sport one isn't that expensive and I'm not afraid about breaking one of my bands while wearing it.