We are experimenting with OpenLayers 2.11 for a new version of the interface on gis.modulo.ro.
The existing interface, based on an older OpenLayers version is very Javascript heavy (so much so that we are probably alienating most of our Internet Explorer users).
As new hiking data is added onto OpenStreetMap (and recently we've had lots of new data thanks to a number of generous donations) the vectors are growing larger, increasing the work required for rendering.
We are considering moving to a interface where the hiking trails are rendered on a transparent tile set instead of Javascript vectors.
This approach is already used in the mobile (iOS/Android) version of the site but with CloudMade's Leaflet; it has the added benefit of allowing a freely moving map (the Javascript vector version is confined within the mountain zone's bounding box as a freely moving map would require too much vector data to be loaded).
Here's a sample of the map in Piatra Craiului: