Suspension is firmer, but still not so firm that it's annoying or uncomfortable. Have done a 3.5hr stint in it and was fine.
You really notice the different power delivery. The S4 (B6) is a really heavy and lazy bugger. The B5 RS4 is quicker and lighter on it's feet. The turbo's give you a good shove when spooled up to. In lower gears above 3k it literally wants to take off.
Considering ARB upgrades, after the wheel spacers to tighten things up again. Will leave the OEM suspension until funds allow and then maybe upgrade that too.
The interior does feel older, not massively or to it's detriment, as Audi's are very nice anyway. But it's little things like the light switch. On the B6 you have a dial/selector near the driver's door? On the B5 you have an extra steering wheel 'stalk' between the indicator stalk and the steering wheel. Just have to re-adjust is all.
Miss anything from the B6 shape? No, not really. Thought I might as it's 2yrs older than the S4 I had, but it's such a special car you tend to get wrapped up in it and not worry about anything else, TBH.
Is it better? Easy to say yes really. Wouldn't knock the S4 though. I'd happily have another S4, but think I'd now miss the turbos. If I had another S4 I would definitely get a Stage III (full exhaust swap + remap) to get up close to 400bhp. The V8 on the S4 makes it a lovely car, and very relaxing to drive, if not a bit heavy. Have learnt a bit more about exhaust mods recently so wouldn't automatically choose Milltek either, for those of you out there thinking about it.
Having only had a few weeks, I can honestly say it is a brilliant car to drive. Performs, and handles brilliantly, and has the looks too. It is also extremely exclusive with so few of them around.
You shouldn't really be put off by mpg figures either. It's alot better than an S4 o/a. I LOVE IT !!