I bought a Yamaha FZ6 last year, best value bike I could find in its class… I’d possibly have gone for an ER6, too, but my previous bike was a Suzuki SV650 and I fancied trying a 4 cylinder bike instead.
Having looked into it extensively (this was about 6 months ago) I came to the conclusion that most of the 4cyl bikes are all much of a muchness, the Honda’s the best quality but also the most expensive (and ugly as…), the Z750 is great, but heavy and crap with a pillion, the GSR600 is pretty much the same as the one I bought, but uglier. And mine came with a year’s free insurance 🙂
If it’s not your only means of transport you might want to check out the Triumph Street Triple and the Ducati Monster as well. (They’re probably both much more reliable than their reputation would seem to suggest, but there’s nothing like a Japanese bike for 100% trouble-free biking!)