These sold like hotcakes at the time, at least in my store. There were many customers who liked the bagless concept, but weren't quite "ready" for a Dyson, with it being a relative newcomer to the market and having such an unusual look. The Vortex gave them the features they wanted, but with a familiar brand name they already trusted, and styling they were more comfortable with. For every customer who is fickle and always searching for the next new thing, there is another who is more conservative and prefers to stick with what they know. Still true to this day, and will probably always remain so.
One of the biggest issues with the Vortex was its timing. It did indeed have several advantages over the DC01 and DC03, which gave it an edge for a very brief period, but those advantages were quickly overshadowed once the DC04 started appearing in full swing. Stole the thunder right out from underneath Hoover again, and that was before the patent row even started.
Me? I liked the Vortex, but could see from the get-go it was best suited to the type of customer who already goes out of their way to look after their things, and would maintain it religiously. It was certainly a lot less fussy than the Electrolux Cyclone Power, which would quickly choke with dust and fail no matter how much you pampered it. The only thing I wasn't particularly keen on was the fact that it was so top heavy, making it tiring on the arm. I don't think the location of the cord winder helped on that front, would have been better if they'd found a way to integrate it underneath the bin.