I've been to Siglo twice and both times it's been a last resort, sub-standard night in the Cowgate.  This is where my friends and I go if The Hive, Cabaret Voltaire, Opium and just about any other club in the area is at maximum capacity.  The drinks are relatively cheap so I can't criticise it on that front.  The problem is that it just isn't fun! For example, the last time I was in there it was pouring with rain (not Siglo's fault, admittedly) and we sheltered ourselves in the bar hoping to just go with the flow and have a great night anyway.  Whilst waiting to be served a creepy, desperate man in his mid-fifties literally tried to chat every one of us up (male and female) until we ascended for the respite of the upstairs dancefloor - or so we thought.  The atmosphere felt threatening and the men's toilets were reminiscent of a crack den.   I have, however, only been to Siglo twice and I'm sure other people have had better experiences of it than I did.  Moreover, it is also a pub which serves decent food during the day.  As a nightclub, however, I certainly don't recommend it.