I suppose I should clear up the debate as to what to use when it comes to installing FS2_Open cause there seems to be some confusion as to what to use and if we sort it out now you can all give out good advice
Basically you have two options. ShivanSPS' all in one pack or a DIY install on top of FS2 retail. I'm not going to say one or the other is the better solution because they both have advantages and disadvantages. If you're new to FS2 or FS2_Open the advantages of ShivanSPS' pack are that everything is easy to install. You install 1.5 followed by 1.8 and 1.9c. IIRC 1.9c get you up to date with everything except for the RC7.8 build you'll need for multiplayer. Shivan's pack also has the advantage of including the FS1 port and Derelict in a ready to play configuration. Simply click the select mod button in the launcher and they're ready to go too.
The only real problems I've heard with Shivan's pack is that it's hard to get some of the updates. 1.5 is easy to get as a torrent but has some rather big flaws in it which require that it is patched to 1.9c. Unfortunately the patches aren't torrented and thus are hard to get.
Bandwidth usage is another problem with Shivans pack if you already have FS2 as it requires that you download about a gig of data which you already have on the FS2 CDs or your existing FS2 install. For some people the convienience of the pack makes it worth it. For instance from the sounds of it cvearl already had the 1.5, 1.8 and 1.9c patches already downloaded. In which case simply deleting his FS2 install and extracting ShivanSPS' pack to the exact same place would have actually been his best bet.
If someone hasn't already downloaded the pack I tell them that they are going to have to spend a lot of bandwidth and leave it up to them to decide what to do. Because although installing FS2_Open is easy for me I can see why it is a daunting process to do it by hand if you're new and it is very doubtful that you'll do as good a job of it as if you'd simply installed the pack
Installing mods is where most people start to fall apart. I doubt that many of the people who have done a DIY installation have a proper working mod.ini like ShivanSPS's pack has. Sure people figure out how to do the Secondarylist thing but how many people actually have the Website and forums buttons working? How many have the picture and blurb configured?

Sure they're only minor things but they do look cool and they do make the SCP install look a lot more professional. One thing that has put off quite a few people is the sheer amount of stuff you need to do to install FS2_Open. ShivanSPS's pack solved a lot of problems initially but the problems patching it to a modern copy have started making it a hassle to use again. Hopefully that will be solved when we release 3.6.9 officially and we get the v2.0 pack from him.