My first couple of purchased systems were Dells... Pentium I 133MHz and then a Pentium II 450MHz. I was completely happy with both systems, until I started getting more into tinkering with PCs and wanted to upgrade some of the components inside. I then discovered newegg, realized I could build them myself for much cheaper then you could buy them, and have been building my systems ever since.
These days, I tend to agree that the large price difference isn't really there anymore between building and purchasing an already built system. I still really enjoy taking the time to research the parts, find the deals, and piece the system together myself. I tend to price everything out at newegg first, and then search around for better deals, which are usually hard to find. I also live close enough to take advantage of some of Microcenter's deals, so I ended up buying a couple parts from them when they are cheaper. So I don't feel there is a need to buy everything from one place.
These days, I tend to agree that the large price difference isn't really there anymore between building and purchasing an already built system. I still really enjoy taking the time to research the parts, find the deals, and piece the system together myself. I tend to price everything out at newegg first, and then search around for better deals, which are usually hard to find. I also live close enough to take advantage of some of Microcenter's deals, so I ended up buying a couple parts from them when they are cheaper. So I don't feel there is a need to buy everything from one place.