Hiya. I've just had mine done, first drive yesterday. To qualify my perception, I've had new shocks and then the 10 usual powerflex bushes, bump stops and cups, droplinks and new springs. It used to crash, bang and clonk over the smallest of bumps (bushes were buggered!) and was getting pretty tiresome. Now the ride is the same but there's no jitteryness, it's properly damped and very controlled, no harshness at all. Although mine were absolutely shot so my frame of reference is a bit off, I can't notice any difference from what I would guess the standard ride is like. I have to say, tyre choice seems to make a big difference too as just before getting it done I had a new set of Avon ZV5s put on which were a big difference in ride from the Bridgestones on it previously, even with knackered bushes. I've also changed the springs, shocks, control arms and droplinks on the front which has made a massive difference too.
I was going through the same dilemma as you as I like to keep original where possible but the fact is if you replace with the pricey OE arm/s now, you'll need new ones in 2-3 years depending on the mileage you do and by then, who knows if you'll be able to get them? Some parts are already difficult to source, e.g. oil cooler. It's a 'do it once and forget' and is considered by nearly everyone as a desirable upgrade not a cheap cheat. Don't believe anyone who tells you it affects the passive rear steering, either, this is entirely dictated by the differing arcs in the geometry, not the give in the bushes.
You can do it yourself, apparently, but I bottled it and gave it to Ferdis in Lytham (Alfatune won't do it). If you're going to do it yourself, advice is to use a press to get the old ones out. There is a cut and hammer method but it looks like a right royal pain. If it had been me I'd have given the arms to a local garage to press the old ones out, couldn't be more than 20-30 quid. You have to remember to grind off the excess weld on the spring arm before inserting the Powerflex bushes to make sure they seat properly and it's best to use lots of white grease, apparently. Other than that it's just disassembly and reassembly with a few weathered nuts and bolts and a lot of patience.
Can you see I researched it to death before I did it...?