|33||33||For the not recommended, this means that while you can get PostGIS to work with those versions, you'll be missing out on some PostGIS functions such as ST_Covers, ST_CoversBy and for PostGIS 1.5 the ST_HausdorffDistance and enhancements to ST_Buffer (both speed and functionality). GEOS 3.1 brought cascade union. GEOS 3.2 brought faster buffering and buffering enhancements, plus numerous enhancements with dealing with tolerance issues when unioning. GEOS 3.3 brought ST_ValidReason, ST_MakeValid etc (in the PostGIS 2.0 releases), so these functions will be disabled in PostGIS 2.0 if you are not running GEOS 3.3. GEOS 3.3. also brought stability fixes for union/buffer not back-ported to 3.2. For PostGIS 1.5, although 3.3 does not add any additional functions, it does fix some crashers involving buffering and unioning not present in other minor releases, so suggested to use that if you can.