To summarise. It is very important for recent disk performance that partitions are aligned on a 1MB/2048 sector boundary. This stops data from sitting astride blocks and killing disk performance. It is especially important with first generation SSDs, as they have poor write performance anyway, and will save your SSD from an early demise (flash memory has limited write cycles).
Windows Vista and above will use the 2048 sector alignment as will Ubuntu, so it isn’t necessary to worry about this issue any more, unless you are installing Windows XP. MAC OS X is the big loser in all of this as it doesn’t care about alignment beyond 4k which may or may not work well depending on the specific block size of your HD/SSD.