As the others have suggested it's much more difficult in HL2 to have such rigid guidelines to try to adhere to; there are now more elements than world and entity polys which can contribute to poor fps performance.

The problem with using +showbudget as a guide is that, having, say, a large world geometry bar can be fine if few cubemap-heavy textures are used, so it would get really confusing as to the 'ideal' a map author should be aiming for.

If there was any mapping standard to be used for HL2 I'd suggest it be mat_wireframe in conjunction with any of the fps readout commands (net_graph or whatever).

Mat_wireframe clearly shows how well (or badly) constructured and optimised a level is. As long as mat_wireframe shows no big issues to address (lots of unseen geometry uneccessarily being rendered etc) and the fps command used gives a reading at least comparable to the Valve levels, the HL2 renderer will likely handle the level fine.

I believe the swap buffer goes up when there are too many potentially visible surfaces at any one location. When the player turns around, whatever that's behind the player is buffered, even though it's not within the VIS.

Have you noticed that when you turn to a highly detailed area of the map at first, the framerates would drop suddenly, but only for a fraction of a second. I believe the engine is buffering the surfaces, so that the next time the player turns around, there wouldn't be any performance hit.

That's my own hypothesis.