I'm completely with you all! I own 6 V-70 systems and 2 V55 systems - all racked and used on theatre productions. They've behaved ok, and unlike others above I haven't had any real RF issues so to speak of. What I have been suffering with massively has been poor battery performance. I have packs that come back after one show with 5 hours remaining and yet others coming back with 20 minutes left. Tests seem to show that the predicted times are about right. Same quality brand batteries and the same results every time. I daren't put them on any key actors for fear that i'll mis-time things and lose their mic. Batteries are now becoming so tight (it's getting worse!) that I need tools to remove probably 50% of batteries that come out of these packs, which is hard work when you've got a quick change to do between a matinee and evening performance.
I have one pack that had a battery leak inside (Opened up a couple of weeks after a hire came back in to find a battery wedged inside and unable to be removed without opening the pack up). It leaked all over the insides and has rotted the ribbon cable and its' pcb connector on the switch/led pcb at the bottom of the pack. I've cleaned it up as best I can and have repaired the ribbon by shortening it by a couple of mm, but it's now becoming a bit intermittent at turning on. Tried sourcing a replacement ribbon cable and pcb via sontec (UK parts source nowadays) but they've been "in production" for the past 4 months.
I'm not at the point of saying do I replace this pack and stick with it, or cut my losses and sell the lot to replace with some proper wireless kit that will stand up to life on the road. These packs haven't worked particularly hard - they've maybe done 10 shows of maybe 10 performances each. I'm hardly a show-a-week rental company!
I also have several packs where the mini xlr has worn to a point where the mic sockets won't latch in anymore. Again, spare parts aren't available and Yamaha UK just don't want to know.
I can't help feeling like the writing is on the wall and that I need to get rid quick. Doubt i'll make anything like my money back though!
As others have said it's a huge shame as this product line could have been really good if it had been supported properly. Great sounding mics and if I had a little more confidence in their battery life i'd definitely be putting them on my principal actors in order to get their great sound quality.