Re: No, you don't wish you'd have bought it.
Depending on the game, it's Not The Same (although some times it's better). Getting the video and audio just right can be tricky, and some games need a much faster system to emulate successfully.
I presume you actually mean Dosbox, rather than the shell that shipped with DOS 5.
For some old games that use Adlib sound, such as the Commander Keen games, I can't tell the difference between Dosbox and physical hardware. For other games that support Roland sound, the use of Munt is not the same as a real Roland sound module, and some graphical tricks just don't work as well under emulation.
Then again, there are the times when Dosbox is better - when a USB joypad just magically appears as an analogue joystick. Alternatively, Copper is a well known demo from the mid nineties that performs various display tricks. It only runs on real hardware with a fixed frequency monitor (some TFTs will work, multiscan CRTs tend not to always), an ET4000AX (but not any other type of ET4000), and a fairly narrow range of processor frequency. Dosbox plays it perfectly!
Personally I think it's worth the effort for some authentic retro gaming, but it did take a while to assemble and configure everything.