I bought my 3.0 pre-facelift about 3.5 years ago now on an 03 plate, to be absolutely honest it wasn't just the engine that swayed me from the smaller engined variants - at the time I was specifically after a pre-facelift and in terms of equipment the 3.0 cars on offer tended to have a fair amount more kit than the 2.5, 2.2 or the 4-pot 2.0 variants (well, these came in from 2005 on I think). Don't get me wrong, the engine is lovely and played a big part in my choice, but it wasn't the only factor in deciding to go for what was (for the 2003 model year) a Z4 with the top engine.
I used mine as a daily driver until I changed jobs and now commute by train to an office in Central London, so it's now my weekend car. As a daily driver a later model 2.0 would have made sense from an economy perspective, but I bought an early 3.0 with my eyes wide open.
Just make sure you're changing because the performance difference is 'enough' to make it worthwhile to you. There's a lot to be said for keeping a car you know (for all it's good and bad points that you now know and appreciate/accept) than getting into another car and finding it disappoints (unknown history, faults that become apparent later).
As for the 'fun' element of driving a less powerful car - I am certain that on a twisty road the 1.6 Focus I owned way back would leave the Z4 trailing if I were magically able to drive both at the same time - I knew that car and drove it 'quickly' a lot of the time, having so much fun in the process. The Z4 3.0 is fun and fast, however if I tried to drive it like I drove that Focus I would probably hurt/kill myself, I will openly admit just don't have the talent. It's the one big reason I've not upgraded to a Z4M, beautiful though they are, I would be terrified to exploit what it is capable of without some decent training. You might find that the smaller engine in that same chassis means you will still have just as much fun, maybe even more - than moving to the 3.0 (unless you're in a straight-line drag race).
I used mine as a daily driver until I changed jobs and now commute by train to an office in Central London, so it's now my weekend car. As a daily driver a later model 2.0 would have made sense from an economy perspective, but I bought an early 3.0 with my eyes wide open.
Just make sure you're changing because the performance difference is 'enough' to make it worthwhile to you. There's a lot to be said for keeping a car you know (for all it's good and bad points that you now know and appreciate/accept) than getting into another car and finding it disappoints (unknown history, faults that become apparent later).
As for the 'fun' element of driving a less powerful car - I am certain that on a twisty road the 1.6 Focus I owned way back would leave the Z4 trailing if I were magically able to drive both at the same time - I knew that car and drove it 'quickly' a lot of the time, having so much fun in the process. The Z4 3.0 is fun and fast, however if I tried to drive it like I drove that Focus I would probably hurt/kill myself, I will openly admit just don't have the talent. It's the one big reason I've not upgraded to a Z4M, beautiful though they are, I would be terrified to exploit what it is capable of without some decent training. You might find that the smaller engine in that same chassis means you will still have just as much fun, maybe even more - than moving to the 3.0 (unless you're in a straight-line drag race).