We have the HS. I love it, I found it awkward to put in the car the first few times, but now it takes me a whole 3 seconds to put in the car. It fits in pretty much every car we've had to out it in, in DH's hyundai work van its a pretty tight fit, but with a bit of wriggling we can get the seatbelt done up and he ain't going anywhere
I really, really wanted a capsule with a base (considering i live in southland, DS is 2 weeks old and its winter) but it hasn't been too bad actually. I don't regret not getting one with a base at all.
I know to fit in the P&T strollers, you have to buy a travel system, which is about $30? or so. I didn't think that was too bad. But I wasn't too worried about buying it, cos I know me, and probably 2 of my cousins will use the travel system + capsule. It might seem a bit of a waste if you don't know anyone else who could use it though??
I think the high sides are the only differences between the HS and the normal one. But I figured for a extra $10 or whatever it was, might as well get the HS one...