I typed my feedback notes before seeing these questions in the form of positives vs negatives so I will copy and paste that anyway as I've written it, then answer these questions one at a time.
Avent pump review
Positives (compared with avent electric and medela manual)
The claim that you can sit back is true, you don't need to hunch over to stop milk from pouring out of the bottom all over your top. This is particularly handy if you want to pump one side while feeding on the other and is the major advantage of this pump.
There is a cap to cover the opening to the funnel. This stops drips pouring out when storing and making everything sticky and smelly. Really handy if, like me, you bring your pump to work in a cool bag. This isn't advertised on the box but is actually a really good feature.
Small bottle size (short and fat rather than tall and thin) is handy if you are pumping on one side with a baby on the other to keep it out of the way.
Negatives
For me personally I didn't get as much milk as I do with my other pumps. But people respond differently to different pumps. We are all individual.
Noisy pumping action compared to medela manual.
Handle too short for even my small hands. You can only use three fingers to pump and your little finger aches from keeping it out of the way.
More parts to wash and harder to put back together than my medela.
Storage disk doesn't attach. I prefer the medela lid so the bottle is secure in a cool bag on the way home from work. This would only be suitable for keeping upright in the fridge/freezer. Not a problem if you transfer straight to a storage bag.
The "petals" looks similar to the areola stimulator from ameda - this might be a positive for some, but I found it very uncomfortable as it caused suction in little sections all around the breast and areola, leaving the whole area tender. Massage would be better than suction here - as in the ameda lactaline attachment.
Not possible to change flange size. There is masses of space, it won't be too small, but my nipple was lost in the massive space and I'm not sure it was the most efficient because of this.
Comes with a newborn bottle. As the packaging admits (in tiny letters), babies should be cup fed, not bottle fed. This can cause nipple confusion and sabotage breastfeeding. I will not use the bottle section, but it is annoying to have to pay for this. I would rather it was sold separately for those who want to use a bottle and the cost of the pump reduced.
Information in the instruction booklet and on the box is inaccurate and could damage the breastfeeding relationship. Avent sell bottles and have an incentive to sell you a pump but encourage you to move to formula so you buy their bottles too, making money out of you twice. Even if you don't take this cynical point of view, understand that they are not breastfeeding experts and don't take advice from this booklet about pumping or breastfeeding.
Examples of inaccuracies and unhelpful language:
Instructions on sterilising and instructions only to use milk from a sterile pump and bottle. (An unnecessary difficult step. Sterilisation between uses is only needed with formula, not breast milk. You will only need this if (when?!) you switch to using formula in (their) bottles.
"do not continue pumping for more than 5 minutes if you do. Not succeed in expressing any milk". (Negative language. When trying to build a supply you might not get anything out, it is the stimulation that matters. Pumping output is not an indicator of supply. Many ibclcs recommend pumping for 10 minutes. Seek. Expert advice.)
Suggests not expressing until breastfeeding is established at 2-4 weeks. (This is far too early. lll recommend 6-8 weeks at least for milk supply to be established and to avoid pumping until then unless needed).
Incorrect storage instructions. Says milk can be stored in the fridge for 48 hours and freezer for 3 months. It is 6 days in fridge, 6 months in freezer.
Says on average pump for 10 minutes to get 60-125ml. (This obsession with numbers and measuring comes from the artificial feeding industry. This is not helpful for the breastfeeding mother.
Information about various avent bottles it is comparable with. Only one tiny font mention that bottles can be damaging and cup feeding is better. No mention of syringe, finger feeding, SNS.
Helping you breastfeed for longer is the tag line on the box. (Assuming you will soon stop, or that it is difficult to keep going, that you will need a pump and bottles to breastfeed. You don't).
All in all, I won't be switching to avent but it might be a useful back up in case mine breaks or if I want to sit back and pump for a little while while feeding my baby in the other side and am not too fussed about output. I would not advise anyone to get advice on breastfeeding from a bottle manufacturer. Have a look on kellymom or get in touch with LLL.