Firstly, It's a 125, the official MCN review irked me a bit because 3/5 engine score does NOT do this bike justice! No, it isn't an arm ripper, what 125 is? It should be compared to other 4 stroke 125's, and under this comparison, the YZF R125 comes out easily on top (I have ridden CBR125's, they are nice little runners but small and slower, much slower).
Onto the main review.
Only downsides are the handling and the value. The stock michellin tyres are LETHAL, change them as soon as you get the bike, and recoup the cost selling the stocks online, personally pirelli sport demons are great. The bike costs a lot, nearly £5,000 brand new this year, BUT, you get what you pay for.
Equipment is perfect, it's only missing a clock, everything else is there that you would need. Quality and reliability is perfect, I ride all winter, and as a tired commuter I didn't strictly obey all anti corrosion advice 2 years in a row now and not a speck of rust or damage so far.
Over the 2 years I have clocked up nearly 16,000 miles, it has never broken down or given me any issues. Gearbox is ridiculously clunky from day 1, but hey, it's a Yamaha, they're notoriously renowned for it.
If you have the cash and will be happy with a 125 for years, buy it now! If like me, you accidentally pass your test first time as you had nothing better to do a couple months into owning this bike and now cannot afford a bigger bike due to the finance payments, buy a 2nd hand one, or a CBR125.