My GF has worked fine, but I did have a number of issues at first. Mainly due to me not understanding properly the brewing process nor the machine's capabilities and shortcomings. A bit of practice sorts out both of these.
As for buying beer instead, there is no way that ���ã500 will buy you better beer than you can make in around five, and certainly under ten brews (I think of them as "brewdays") with a brewing set-up, however sourced.
Regarding which one to go for, there are lots of videos on U-tube of blokes making a beer using the BM, the GF, and all the others. All seem to be keen on the one they have themselves and you might reach some conclusions from watching them.
It took me five brews in the Grainfather to get to producing better beer than I can buy in the supermarket.
I had only done kits before that and I only did about five of them.
The best tips for brewing with the Grainfather, I found on this forum.
Try to get the courser grains into the mash tube first, dust on top.
Dough in well, creating quite a wet mash.
Leave a small gap between the top plate and grain.
Start the pump with just a trickle to start and very slowly over five to ten minutes increase the flow, so either nothing or a very small amount goes down the overflow. This will stop it compacting.
Remove the top plate and give it a stir half way into mashing period.
Increase flow slowly again.
Push top plate to touching grain to sparge.
I had a very smooth brew day using these tips yesterday.
One thing which I have learnt to be very important in getting good beer, is to learn about your brewing water and how to adjust it to suit the beer.
I never knew when I started all grain brewing, how much there is to learn.
Bit like gardening, you could be learning for a lifetime.