Are they that bad? I’ve been interested in buying a cordless vacuum, and the Dyson ones seem to top all the review lists (e.g. Wirecutter). What are some good alternatives?
The Dyson 'bagless' idea is a bit of a sham. Yes they work, but they don't work that well. They don't make as much suction as their bagged competitors so they cheat and use smaller orifices to increase suction instead of by having a larger motor or alternative design. Then in order to have 'like new' performance all the time you have to continually wash (which doesn't really clean well enough) or replace filters.
Some people love them but they don't make sense to me. If I'm emptying my vacuum I'm going to empty it into a bag anyway so I may as well use a bagged vacuum that works more consistently and doesn't throw dust everywhere.
It's not a sham, different use cases call for different things.
The suction is also pretty poor, however it makes up for it by having a roller in the vacuum head which picks up the dirt.
If you have anyone in the house with long hair its almost unusable as the roller will be clogged up after a single vacuum. A traditional vacuum with better suction and no roller wont have this issue.
On the plus side they are light and manoeuvrable, and the wall mount means you always keep it charged.
It's made of really cheap plastic and has cracked in a few places.
Being bagless is good in that I can see what it's collected but bad in that when come to empty it the dust I'm allergic to goes everywhere. (If only someone would invent a bag to keep the dust in eh?).
The cordless one does not quite match the suction, but it's so much more convenient and sufficient nonetheless.
Dyson aren't awful but they're definitely overpriced.