There are other solutions to not being able to fit a carrycot in the boot of your car :)
You can use a sling until baby is older.
You can get a buggy with a proper lie flat mode - some good suggestions above, also look at Mutsy Evo, Cybex Priam, Cybex Balios S Lux, Maxi Cosi Leona, Joie Chrome, Finiti, Aeria etc. Some of these fold small enough to fit into a Suzuki Swift boot (this is what we had - we couldn't fit a carrycot in).
You can place a carrycot on the back seat, next to the baby in their car seat - if you don't have other children. If you do plan to have more children in the future you could plan to upgrade the car by the time the second one is born.
You can get what they call a "soft carrycot" and place into various strollers. (Just google soft carrycot for examples or soft carrycot + brand of stroller you like)
You could purchase one of the car cot type seats (e.g. Maxi Cosi Jade) and place on a pushchair set to create a travel sysrem. These do not last as long as other baby car seats, but when outgrown, baby will be able to sit up and therefore they will fit a normal buggy seat and they will also be fine in the fixed or rotating car seats that stay in the car, like Avionaut Sky or Britax Dualfix.
The Doona is OK as a car seat/stroller combo, and definitely has a role for people who do a lot of in/out of cars, but it won't replace a proper lie flat pram, and it's probably not that much more convenient than getting a combo of any universal infant carrier (there are various brands that go on universal pram adapters e.g. Cybex, Maxi Cosi, Britax, Joie) and a lightweight buggy such as Bugaboo Bee or Babyzen Yoyo. You can get car seats which have much better positioning for new babies, such as the Maxi Cosi ones with the nice inserts (pebble series, or Cabriofix i-size is a cheaper option), Avionaut Pixel/Cosmo which is very ergonomic, or lie flat type seats (which aren't REALLY as flat as a carrycot so shouldn't replace the carrycot totally, but are better than the normal 30ish degree car seat angle) like Britax Babysafe 5Z, Cybex Cloud T, Joie i-Level etc. The new Besafe Beyond set looks great too.
The crash test isn't awful, it's not so bad that I'd say avoid it, but it isn't as good as some other brands especially for side impact protection. I've also heard people say that it's heavy to lift in and out of the car which sort of defeats the point of it, and the wheels are small so aren't great for any terrain other than airports, shopping centres, very smooth pavement etc. (This will be the same for any of the ultracompact buggies - you need bigger wheels for more terrain capability).
In terms of time in car seats the recommendations are that newborns up to 4 weeks should have a break from the car seat every 30 minutes, and after this age it's 2 hours after which they need a break. Also they should not spend too much of their day in a restricted position (which a car seat is) - they need plenty of time on a flat surface to roll around and practice their development - rolling, stretching, moving, kicking. Being aware of these limits is important regardless of which car seat you have 
I think it's totally possible to have a balance - people get very black and white about this issue. It's really up to you to think about what is likely to work best for you.
If you have a locak stockist it is a good idea to go and look at the seat in person, see if they have a weighted doll you can put in it and practice lifting it up and doing the wheels etc. Compare the angle to other car seats. See how the other car seats go onto a pram and how that feels - most decent sized baby shops will have all these things to try out, so go and have a play. It's a large amount of money so it's a good idea to try things out first.