I bought this low cost DSO150 ("DSO Shell") pocket scope from AliExpress for under $20 incl shipping.
http://www.aliexpress.com/wholesale?catId=0&SearchTexct=dso-shell
This video is about debugging techniques for when your QCX construction didn't quite result in a working QCX. The methods described and demonstrated with the cheap 'scope are also applicable to more advanced 'scopes. See also the QCX troubleshooting page
This video is equally applicable to both the QCX and QCX+ transceiver kits, which share the same circuit design and firmware, but have a different physical implementation.
Also shown, are how to use a cheap DVM, and even the built-in DVM on the QCX, to carry out debugging of the Receiver section.
Finally I transmitted some CQs on 40m CW and after the third CQ, had a nice QSO with Nick LZ1NG.