The system would probably have been a much greater success if
Sinclair had put a floppy disk drive in it instead of using an abortion by the name of
microdrives. These were a small plastic cartridge with a continuous loop of
magnetic tape in them. They were very
expensive (five pounds each initially),
slow, and
unreliable.
The problem was that Sinclair owned the patents for microdrives and decided to use them rather that putting a single 3" or 3.5" floppy drive in (which would supposedly have cost him the same).
There was also a problem that the BIOS was originally planned to be only 32K and so when the operating system (QDOS) required 48K the first QLs shipped with a dongle that plugged in the back and supplied the other 16K of ROM. They did manage to release a version a few months later with no dongle.
It was the shipping of this computer over 3 months late after they had taken orders with a promise of shipment within 28 days that did a lot to damage Sinclair's reputation.