I, well, my gf, drives a mk4 R32 as a daily driver. Although not a mk5 perhaps I can give you an idea of what the mk4 is like in certain aspects. Yes it has a V6 is responsive and it picks up quickly.... But the car feels heavy. The steering is very light, same with the handful of Golfs I've driven and it's well put together. It's nearly 9 years old and there's hardly any squeaks or rattles. But did I mention that it feels heavy? Its not nimble is perhaps a better way of describing it.
Exhaust note is nice to a point but motorway cruising can be a bit tiresome if at a certain rev range with exhaust drone. Not sure if mk5s would be the same. It will come as no surprise and as previously mentioned on here that it's thirsty. In my experience I see high teen mpg when on a bit of a hoon, and low to mid 20s on a cruise. 30 is but a dream. My gf finds a few more mpg in each category. Servicing seems relatively inexpensive and touch wood I've not had any serious trouble.
Couple of other points, assuming mk5 is the same. You won't win any traffic light grand prixs against other hot hatches, if that's what you're after. You need to hit 3rd gear to reach 60.... But, this does mean it is fantastic on the move and 2nd, 3rd and 4th make overtaking quite simple. 6th gear is responsive at motorway speeds if you need a quick change of pace.
Would I buy another? I genuinely dont know. I like the mk4 Golf shape in sportier models but theyre getting old now. Mk5 is a bit funny looking for me and in R32 variant I think the exhausts look a little odd and the shape doesn't quite do it, but they attract less attention as a result, attracting attention is something my gf doesn't like about the mk4. It's a well put together car, but beware of the spec you buy, there are some lower spec'd mk5 R32s out there with regard to interior and on a like for like comparison this is where you would see a positive difference vs a GTI in my opinion.
A change of job role has meant more miles for her, so fuel is more of a consideration. As nice as the V6 is, if I were buying again I'd opt for a newer S3. But I have a real issue. I like hatchbacks, their practicability (R32 great for a run to the tip or Ikea), but I like things like sunroofs, leather heated seats etc. I don't like OTT body kit, excessive lights and generl brashness that blights many cars. So for me the "quality hot hatch" choice is slim. Try finding a 5 door S3 with sunroof. Nigh on impossible, but if I was in the market for a replacement this is where I'd look (presuming diesel is ruled out, then then find a nice looking sporty diesel hatch that's nota 1 series, which do not do it for me).
Only way to see if you like it is take one out. They are more of a stable b road bomber than a traffic light hot hatch. V6 noise coming at the cost of 22mpg.
Typed on iPhone. Please excuse spelling and grammar gremlins.