Ive got one and to be honest its a good little genny. They used to be about £60 but now theyre silly money at £100.
I ran mine for most of last year and the year before and Ive only had two problems. One is that the flywheel spun and I had to put a new key on the shaft, the other is the starter claw which broke, but this was due to trying to start it when it spun the flywheel.
Power wise we had it powering an ENTIRE Keighley meeting with around 15 drivers and all of race control and it didn't miss a beat.
I got a new £280 suitcase 4stroke genny at the end of last year with all the fancy sine wave stuff and to be honest Its not much, if any quieter and Ive noticed no difference in power delivery. Infact the new genny cuts off when it gets near to the limit where the old one just chugged on.
In regards to voltage they're not super consistant when not under alot of load but I set mine to give between 210v and 240v and as most things that run from a transformer take between 110 and 240v it was never a problem.
Theyre not perfect and at £100 its too much money but if you're on a budget and can get one for £40/50 then they'll do the job and do it well. If you have the cash then get a suitcase genny. The choice is yours