As above, make sure they are from a reputable manufacturer and follow the recommended procedure with regards to correct torques, and re-torquing after a few hundred miles. Use a wire brush and make sure the bearing face between the hub and the spacer is clean. You can also use copper grease and thread lock if you want.
I'm fairly certain spacers aren't going to damage the suspension. I thought about this quite a bit before I put them on mine. The difference in the increased track is pretty negligible in terms of leverage. Think of it this way, how much easier would it be to do up a bolt using a 25mm long bar as opposed to by hand? If anything at all it would be a tiny amount, and when you relate that back to the suspension it should all be well within the load tolerance of all the components in the suspension that it would have any effect on. Obviously if you put on whacking great spacers and extended the arches, the strain on the components would grow exponentially the wider the track. Most of the horror stories about spacers I have read is guys in the US putting them on big 4x4's and trucks and increasing the track by 70mm a side or something ridiculous, which I would definitely agree would have an adverse effect on the suspension enough to push something to break. Yes the amount you need to increase the track on these cars will increase the strain on the suspension, but by three parts of f*** all, and I would argue not enough to cause component failure more than normal wear and tear.
I thought the H&R ones I got were really nice bits of kit for the money. I've got toolmakers and a CNC shop at my disposal with work, so I thought about making some. But once I weighed up the time it would take modelling them, programming the CNC, buying the bolts and the helicoils and anodising the spacers after machining, it really wasn't worth doing when its like £340 for a full set.