Here is the WGA Qiagen REPLIg ultra fast PROTOCOL.
I added also general information (mostly from the Qiagen site) about the REPLI-g method of amplification and about other similar Qiagen kits available.

WHY using this protocol -> if you need to increase the amount of your genomic DNA for downstream reactions.
Note: there are additional Qiagen kits, at least for the amplification of RNA (they seem to give great results) and Mt DNA (I don’t know anyone who used it).
STARTING MATERIAL -> you can use this protocol if you have at least 10ng of purified genomic DNA (it’s better though to have at least 40ng). The average genomic DNA fragment size has to be 2kb or more. If you have highly fragmented DNA I think you should increase the starting amount, but check the Qiagen site for more details (you can find the link in the word file).
WHAT you end up with -> way more DNA! If you look at the figure on page 2 of the word file, you can see that the ultra-fast kit should give 10ug DNA, but I had lower yield (around 1ug). Note that I did not have information about the quality of my samples, so this could have been the limiting factor. The figure shows also the mini- and midi-kit procedures. The work you have to do is the same, there is only a difference in the incubation time. According to this figure, the mini-kit seems to have the same yield as the ultra-fast kit but people who tried it said that it works better (in the sense of a higher yield). The midi kit seems to give up to 40ug.