Yup I totally agree Jafo, bootskins may be considered a simple form of skinning but it makes you appreciate limits such as working with an image with a max.size of 640x480, limited to using 16 colors so you have to be creative in maintaining image detail, creating progress bars that work well with the bootskin bkgrnd image and use the same colors and getting used to testing, testing & more testing before uploading your skin to the site to share with others. And at the same time you're honing skills in your respective image/graphic editing application (photoshop, imageready, fireworks, psp, gimp, paint, etc.) and with regular use getting better & more accustomed to working in a graphic editing environment.
Plus with the windows os being problematic for a majority of users (myself included on many occasions), reboots become a near guaranteed requirement so if you need to reboot you may as well do it in style.
What also helps more than anything else though is having a great website like wincustomize.com that you can showcase your creations and receiving feedback (good & bad) from so many other website users just like yourself so that you can continue to improve & upload more work. That process helped me alot and made me brave enough to tackle on another skinning category and once you get over that initial hesitation, it becomes clear that you if you put in the required amount of time, any skinning project is possible. No one starts off as an expert and everyone's original work usually shows this as fact, repetition & persistence improves
everyone's personal skill-set if you're determined enough to keep at it.
I would encourage everyone to get started in a similar fashion if they're interested in getting involved in skinning & windows customization. No one (at least for the most of us) will start submitting work that's worth 5 stars on this website but if you keep at it, after a few years it's possible to attain the level of workmanship that warrants that kind of rating.
Thank you to everyone for the great comments & feedback, as always it's an honor & pleasure to be part of this great online community.