I use a shubb sliding capo. I just got used to tucking my thumb under the neck and I have no problem at all with it being in the way. I do get up on the neck quite a bit. It changes faster than a spike and reaches for seven (!) frets. I think it's the longest they make. My experience with railroad spikes is that if you have a fairly low action as I do, they tend to buzz. I'd agree that the spikes look better, particularly if you're concerned about an "authentic" look.
:-),
chip