Yes, if you have multiple cubemaps on the map, the cubemap that is closest to you will be used for reflections, you can however manually specify cubemaps for bsp brushes to prevent obvious swapping between cubemaps.

Cubemaps aren't as good as real time reflections (they don't consume as much performance either ;)), but well placed cubemaps at a high resolution (128 or above) can look just as good!

Well I did a bit of roaming around other maps, I think I need to pay more attention to where the cubemaps are located in relation to eachother. I'll try setting the map to 128 like you suggested, and make sure there is another one at most 256 away, that should stop the inside/outside bleeding perhaps?

As for the xbow lens I think I overreacted a bit, somehow I was expecting real time reflection. There is an example of what I mean by "wall-bleeding" n Lockdown: Under the charger room, near the battery and hpack, if you walk around in there with the xbow, at one point you will see a relection of the charger room itself ( another curious thing about the sdk version of that map is that every piece of glass in the "gateways" has a cubemap by it, but I could see anything spectacular moving around in there ).

Thanks for the bsp offer, this map has a ton of custom content, but would be a pain really, I'm hoping to delay the pakratting till later. Reason I haven't posted any WIP pics here is because it's supposed to be for the hl2dmuni map contest, they have a loose NDA about these things.

I guess really that i was just sloppy with my placement, I did find another example of bleeding in another one of my maps, I'm sure there are plenty out there. Would be nice to have a hard and fast rule though.

Hmm, this doesn't look normal to me buddy, especially that second screenshot. It defiantly looks like a graphical error to me, I really think its your graphics card man, you have been having so many problems with Half-Life 2.

The only thing I can think of is set the resolution of the cubemaps to 128x128 or higher, if you get an error when buildingcubemaps, than you might have to lower your cubemap resolution. Once you have set your cubemap resolution as high as you can, compiled the map and compiled the cubemaps, reload the level (just incase, most mods/games you don't have to restart the level), than use the console command impulse 81. The reflection you see in the ball should look like the surroundings where the cubemap is located.

Another thing to try is upload the bsp somewhere and I can give it a quick test, I know cubemaps work fine on my pc.

Oh, make sure you compile with at least fast vis, fast vis doesn't take long at all on even the most complicated of maps.