What TallPaul_S says is quite true though. Power is great but where the power delivers is just as important. I was defending my IL4 in another discussion with him a while back - it is unusually very torquey low down and incredibly smooth all the way through the rev range.
But if you want to access all the power at the top end, then those are indeed licence-losing speeds. Mine's entering the nice power band in second gear at about the point it hits 70 mph. A v twin will get you to that power band much earlier, the trade-off being that they normally aren't much fun to ride at slower speeds.
If you've gone from 33 to 73 bhp and haven't really noticed the difference then likely you're riding down low in the rev range and a powerful v twin will make the biggest impact to you. It is just personal choice though, and I'm at the point where I'm fed up with lumpy low down v twins and love, when I can, hearing the IL4 sing at the top end. Give it another few years and I'll probably be back on a big v twin, saying they're the best thing since sliced bread.
Took it out at the weekend for a good ride, was certainly a relatively high revs for lots of it
Tbh, that does concern me with IL4's, having to have them at the top end for the 'real' power. I'll take a few out for test rides and see how they are. Tbh, I do like the torque of my SV
Nearly forgot to properly reply to this
I've did a few test rides last summer, including a 140bhp IL4 and a 1000cc 100bhp v-twin - the IL4 was the GSX-S1000 and the v-twin was the new v-strom 1000. Very, very different bikes, but I was actually riding faster on the v-strom! Partly because it was so quiet, and partly because the longer travel suspension gave it a 'magic carpet' type ride, and also the fairing meant that 50mph felt like 30, and 70 felt like 50...
On the GSX-S1000 because it's a proper naked you feel the wind and know when you're going fast, because you can feel it. The GSX-S1000 only revs to 11-12k rpm, so it's a very different beast to something like a fireblade or any other 1000cc superbike at 14-15k rpm. However the biggest difference is the fairing - on a naked bike at over 80mph, the pressure on your chest/neck/helmet is a lot, and it's a bit of a licence saver IMO. On a faired bike, that same speed feels a lot slower because you don't have the wind on you, meaning on a litre faired bike you can go up 2-3 gears fairly quickly and be doing over a ton without really noticing.
In the end, it's all down to self restraint - I don't think I'd ever have a litre IL4 sportsbike becuase it would be so easy to lose your licence (and honestly I don't think I'd ever go above 10k rpm on the road
). Litre IL4 naked? Not a problem. I actually thought when I test rode the GSX-S1000 that i'd be quite happy commuting on it. Litre V-twin sportsbike? again, not a problem, as shortshifting through the gears using the low down torque is fun
1000cc+ sports tourer, again not such a problem, although stuff like the k1300s are ballistically fast, they might only rev to 11k rpm but the gearing is very long (2nd gear redline about 90mph) but that's also what makes makes such good tourers.
That brings me to another thing that abyss pointed out - big v-twins don't make good town bikes! I'd never commute on a 1000cc v-twin. A 750/800cc, yes, but not a 1000cc+ - you'd be feathering the clutch all day in traffic. An IL4 makes a perfect commuter as most will trundle along at 2000rpm. On my little 400, I can be in 2nd gear at little more than walking pace with the clutch released, and 30mph in 6th gear 3k rpm.
Just remember that any bike over 1000cc, whether it's a v-twin or IL4 will be VERY fast, a lot of the character comes down to the gearing too - like the 1290 superduke which is 170bhp, but has very short gearing, 2nd gear redline is only 83mph. Makes all the power usable... not sure about all the torque though!
my CB400 2nd gear redline is 65-70mph!! That's a bike with nearly a quarter the power
on a fireblade, 2nd gear redline is 120mph.
http://www.gearingcommander.com/ is a good website to look at, it's got stock gearing for a lot of bikes.
Get some test rides over summer, on a few different engine types and bike types, and see what you like
Just maybe think about getting a naked bike if you're not sure you can restrain yourself