Despite the fact I've only owned the mics for two days now I can honestly say they're a sound investment for anyone who seems to whip Singstar out at every social event.
The mics come with 4 AA Sony batteries (2 per mic), a usb receiver with lead and a quaint little pouch for your mics. From what I've heard the batteries last for a long time as people who have been trialing the mics since christmas time say they are still on the original Sony batteries provided. The manual also recommends the use of rechargeable batteries to anyone concerned.
After a couple of days of solid use I haven't experienced a problem whatsoever (eg synch, buzzing) however the true test will come when I take them to a party later this week.
I think it's unfair that people slate the mics for being a little pricey when the competitor Lips is only marginally cheaper. You've also got to take into account that you're paying for the quality that is Singstar - after all, Lips lacks custom video features, a thriving online community and many songs in the store. But then I guess Lips does offer you the chance to tip your mic upside down and bang along to drums... Sony are merely doing what the majority asked for, mics without wires, simple. If you are taken in by new gimmicks, the next iteration of Singstar (Pop Edition) will offer voice recognition where you can say a song and it'll pop up, avoiding the need to pick up the pad.
If wires really do get on your nerves then I'd highly recommend this product, but don't expect any sort of overhaul, it's just your typical Singstar microphone.