- in response to your questions:
1) Yes. They have Visionarry Mapping (Plus) Technology (build-in camera), so they're are able to save the location and after recharging return to the place where there was "break". Also, mapping technology enables them to return straight to the charging dock, moving across the shortest way - just like Neato.
2) Yes, that's true. The latest generation is equipped with Li-Ion battery (unlike Ni-Mh used in prev gen), which gives a total time of 100 min (unlike 90 min in prev gen), but it take up to 3 hr to recharge (2 hr in prev gen). Btw, Samsung states that this 'type' of battery should last longer (more charging/recharging cycles) than 'standard' Ni-Mh type.
3) I have really no idea
I was only in possesion of SR8855 and now I own SR8895.
4) Worth to add that in 4th gen there are 'silent' models. There is 'only' 2dB gap between them and new "S" line (62 dB vs 60 dB). I find SR8895 (62dB) a LOT quieter than SR8855 (73dB). Not sure if these 2dB makes such a BIG difference.
Moreover, 5th gen is equipped with dust sensor (auto turbo-mode activation), sound mute, and "ultra" low design. It has smaller dust bin (0.3L vs 0.6L), but wider main brush (20cm vs 16cm).
In my own opinion the new pleated
HEPA filter can be harder to clean (all those hard to reach pleats...) - if you have ever tried to thoroughly clean such filter under tap, you will know what I talk about
Oh and I don't even want to talk how it's important to clean these things (we all know that they're most important things to trap all the dust...what lives and is borned behind its fibres? grrr...). I wash mine with hot water and bleach/liquid detergent - it always looks and smells like new!
5) There was reported that some models from 4th gen (SR8845/SR8855) manufacutered in 2010/2011, had some problems with correct navigation, losting it's map, working in bad light conditions, and had broken wires in drive wheels circuitry.
past: Samsung SR8855/SR8895 (bad rotor) Neato XV-11/XV-15 Roomba 780 (bad battery) Scooba 385 Roomba 530 2x Scooba 230 (broken bladder; 1yr of use -> $300 dump to trash - not worth any $)
current: Roomba 620 (bad CHM; repaired u/warranty)