Specifically, they have had trouble exploiting its advertised "plug-straight- in-to-the-internet" capability, because its built-in modem - the device that sends data over phone lines - actually runs too fast for some telecoms systems. The result: no internet connection.
Other buyers have had problems connecting printers to the iMac, because the printer's manufacturer, Epson, had to scramble to write the software to fit Apple's radical new "USB" system for connecting gadgets to the pounds 999 iMac, launched in the UK last month.
Users also face a Catch-22 in solving the modem problem. Apple's decision to omit a floppy disk drive from the machine means that, although a software "patch" which tells the modem to run slower is available, you can only download it from Apple's web site.
But just as the original Catch-22 meant you couldn't be excused flying unless you were mad, but wanting to be excused flying meant you were sane, with the iMac you can't make the connection because of the problems you're having - and if you could make connection, you wouldn't need the patch.
Among those to discover this was Ian Cargill, who found that his new iMac's connection to his Internet Service Provider (ISP), Belfast-based Direct Net, kept cutting out. Direct Net confirmed last week that the problem lay with its telephone supplier, which could not support the speed at which the iMac modem runs.
Mr Cargill found that the only way around the problem was to download the "patch" on another computer and then email it to his iMac. "It connected to the net just long enough for the emailed file to be retrieved... The connection is now rock solid," he said.
Interest in the machine remains high. By last week, Apple UK had sold "several thousand". On Wednesday, its US headquarters will announce financial results expected to show that for the first time in years, Apple has been profitable in every financial quarter.
In the US the iMac was the second-best selling personal computer in August, although launched only until mid-month.Reuse content