Lots of people have mentioned lots of problems with dual booting. Personally I have seen none. You mentioned a triple boot as sort of a joke. That is precisely what I do, although I spend 99.9% of my time in XP.

You are correct that partitioning tools are an absolute joke in Vista (at least the Home Premium version, I haven't tried Business or Ultimate). An extremely cost effective and powerful solution to this particular problem is to burn yourself an Ubuntu CD. Most people's eyes roll back in their heads at this point, but the reality is that it's a very simple solution. After you've burned the CD, you stick it in your computer and boot from the CD drive. Pick the option to start Ubuntu without changing your computer. Since it loads the entire operating system into your ram, it will take a few minutes to load.

Once it does, you open a terminal window and type in "sudo gparted".

gparted is a Linux partitioning program and it is very powerful. It will see most (not all) hidden partitions even, something that Microsoft operating systems are not capable of doing.

One thing that you may run into are primary partitions vs extended partitions. There can be a maximum of four primary partitions on any hard drive. Every Microsoft operating system needs to be installed on a primary partition. The problem with this is that many new computers have hidden primary partitions that store backup or recovery information. Dell computers may also store Media Direct (useless in my opinion) on a hidden primary partition. It doesn't take long for these primary partitions being used for proprietary purposes to limit the ability to dual boot because you're bumping up against the 4 primary partition limit.

If this is a difficulty for you, you'll have to decide whether you want the recovery partition (also worthless as far as I can tell) or Media Direct partition or whatever else. If you feel you can live without them, then you can be pretty flexible by deleting everything you see with your Ubuntu CD or whatever other partitioning software you choose to use.

If you decide to use the Ubuntu CD, you can also format it, but I probably wouldn't. For no particular reason, I've always done the partitioning w/ the Linux live CD and the formating during the Windows installation process (or afterwards from within Windows if you have a storage partition to format). I guess my (possibly flawed) reason is that for a long time Linux didn't understand NTFS, and then for awhile after that, it kinda understood it and would maybe fry stuff if you tried to edit anything on an NTFS partition, maybe wouldn't. I think that's all been resolved now, but I just felt more comfortable letting Windows do the formatting portion of stuff.

The only real problem that I've ever had dual booting has been in regards to different file systems. If you wanted to run Win98SE and either XP or Vista, I might have some cautions for you because obviously Win98SE isn't going to be able to read stuff on the NTFS partitions so you'd have to have a swap partiton that had a file system of the least common denominator, FAT32. However, with Vista and XP this isn't something that works it's way into the equation unless you intentionally choose FAT32 for the XP installation (which I doubt you're doing).

You mentioned security. Security is an issue. As you're probably aware, if you want your data to be protected, it doesn't matter how good of a password you put on your login screen and how careful you are in assigning administrative priveledges, etc, if someone comes to your house and flat our steals your hard drive and installs it on their computer as a slave drive, they can access all your files that were not encrypted.

Similarly, if you have excellent Vista security set up, but poor XP security, you can have sensitive files stored on the Vista partition that would be next to impossible to access from within Vista unless you had the correct priveledges but a 2 year old could boot into XP and totally wipe out your Vista partition with a few clicks.

All in all though, I would say that dual booting has been a very good transitional tool for me over the years. Actually, ever since I had my first computer (which I built) I've always had two operating systems on it. Usually I'm pretty much tied to one of those operating systems, but there also usually ends up being a time where it's very handy to have the second operating system. Say XP gets hosed, instead of spending an hour re-installing just so I can check my email, I shut it off, turn it back on and boot into Vista and check my email. As with anything though, YMMV.