The current Second Arrow has no change as far as the flexibility of the vestibule goes. I would be very surprised if the First Arrow had changed in that regard.
It makes a significant difference as far as I'm concerned (especially if you have stuff in the vestibule you're not forced to crawl over it). But as you say, each to his own.
Re sitting up at the far end:
Yeah, that's not something I miss being solo (haven't tried First Arrow, it is a lot larger). Both those tents have a reasonably heavy taper - they are designed for room at the shoulder where it is needed.
Re bulk, I don't find it too bad but you could reduce bulk by leaving bags or replacing with lightweight ones:
They give you 2 pole sleeves where most give one, proper pegs which are MUCH stronger than is usually provided (but bulkier) and the tent and poles bag (fabric is plenty strong enough for poles to be carried outside the pack through thick scrub without damage to the bag)are significantly heavier than for most other manufacturers (as is the ground fabric). At 30D for the fly (siliconised version), the fabric is on par with many others for "weight" but not in the same league (for better or worse -- I would argue that 30D is "better" for most people) as some of the gossamer fabrics available (eg. some manufacturers are now using 15D which obviously requires more care and is not as long wearing - all things being equal - as 30D).