I use spurs, and they are absolutely not cruel. If they are used incorrectly, or by someone less experienced, then they certainly can be. But, inherently and if used correctly, spurs are certainly not cruel.
I use spurs to get my horse to engage his hind end a bit more effectively.
It may help in 'waking your horse' up a bit, and encouraging him to listen to your leg. This is all under the assumption that you already know how to use your leg effectively (you don't sound like a particularly novice rider).
On my horse I use a "Prince of Wales". It's not a particularly harsh spur.
The sensitivity of the internet baffles me.