I own an Alessi ankle holster for a Sig p239 in 9mm and as far as ankle holsters go, it's the most comfortable I've come across. Lou doesn't advise using an ankle holster for single action, cocked and locked autos as the action collects a lot of lint/junk but he does make them for those guns. I wouldn't suggest it for a 1911 with a barrel longer than 3".
I have an Alessi ankle holster for a Colt Detective Special. I do not use it regularly, but you can get used to the weight for casual activity. However, I can't imagine using it for something that is heavier or has a large size. No matter how tight you attach it, mine will ride down until it's resting against the top edge of my shoe. This usually isn't a problem.
That said, I have a G26 and I've considered the Galco rig with the ankle strap for it.
I have one for a Glock 26, and really think that it is excellent. The extra weight is bearable, but that is the price that you pay for having an 11 round 9mm carried there. It's so well made, I feel I need to order more of his work.
I have an Alessi ankle holster for a Colt Officers Model that I have used fairly often. I carried it as a spare to my full size 1911 duty gun. Mine came with a pull through snap that I cut off. I prefer open top, as both of my other Alessi ankle holsters are set up that way. I find the retention of the firearm is fine with an open top. I was using a LW officers model and I did not feel burdened carrying it. Its all in what you get yourself used to doing. Carry it for a couple weeks and you will start to realize when its not there, not when it is. I also find the calf straps to be a gimmick that is unnecessary with a quality ankle holster. It helps support the weight of the gun in a holster that cannot support the weight of the gun by itself. It causes the gun to rock from the extra support point and the holster does not fit nearly as snug to your ankle which causes it to print more.
I carry a Glock 27 in an Alessi every day now, since the department started issuing and requiring us to carry their Glock 22. Ive been carrying Alessi ankle holsters for almost 15 years now. Ive tried most of the factory ones and a few custom makers models. Alessi is the only one I would recommend.