I've never had a Dyson before so I was excited to get one. Overall I would have to say I am disappointed but I can see some advantages for certain groups of consumers.
On the positive side, the machine is tiny. If you live in a small place with limited storage space, as I do, this is a definite plus. It tucks away into a very small space (a deep kitchen drawer would do it) and the parts detach very easily - again, useful for storage. The design is very pleasing, as you might expect, and it will get into very narrow spaces even with the main floor tool attached. It feels very solid and well constructed. I can't see the tube breaking for example - which has happened with most of my previous vacuums.I have a decent size one bed flat and I vacuum most days as I have a cat. I find the drum fine. It needs emptying once a week on average, and the mechanism is very simple and requires no strength or dexterity. It is also very lightweight.
On the negative side, the main problem I have is that it doesn't pick up as well as I would like. Even on wooden floors, I have to go over things twice, and on rugs I have to go over things four or five times and sometimes resort to getting on my knees and using the small tool attachments. This would be a definite disadvantage for my Mum who can't get on her knees any more. The main floor tool is a strange design, with a slot in the centre that causes the machine to miss things. I also find the handle a strange addition - although it is comfortable to hold, it doesn't allow me to exert enough pressure and I often find myself holding the tube instead - it seems extraneous to me.
So all in all - this is a reasonable vacuum. It has some design points that don't suit me, but some features that are very helpful. For the price I think you can do better. I've definitely had more effective machines in the past that weren't much bigger.
Additional note: I've had the dyson for around six months now and I would just add that it's really important to wash out all of the filters regularly - the machine picks up better if you do. I'm really torn by this vacuum and trying to give a fair review - which is why I'm revisiting. I have to say, I do rather like this machine with more use - I think because it is SO light and packs away so small. It is not the best I've had in terms of pick-up, but it has really stood the test of time, daily use and no damage, wear and tear, lessening of effectiveness... which I can't say about previous vacs. So I think in summary - the quality is excellent, it is super compact, the pick-up is ok to good.