So, are the real budget lavs really useable or do they suffer from too much noise or interference.

I talking,

Audio Technica W88 13 829

Sony WCS 999

Azden WLX PRO

Has anyone had real world experiences with any of these systems. It’s difficult for me to find some of these systems where I live apart from the Azden, so I might have to end up with the WLX PRO.

I have a Sony ECM 150 lav that when directly connected to my camera produces really good results. But I need a wireless system now. If I used my ECM 150 with the Azden WLX PRO system would that work well. What’s the limiting item with budget wireless systems, the mic or the radio system, as if it’s the mic I can use my ECM 150.

It's the radio that's the limiting factor, though at those system's price point the included mic capsules are also going to be less than sterling. The general consensus is the Sennheiser G2 (or now G3) marks the lower boundary of the range of mics one ought to consider for serious work.

As Steve says, the RF system is the limiting factor. The mics on the cheaper systems tend to be rather bad too with the exception of this:
Audio-Technica | Pro 88W - Camera Mountable VHF | W88-13-830 (http://www.bhphotovideo.com/c/product/68055-REG/Audio_Technica_W88_13_830_Pro_88W_Camera.html)

You will notice that it is the same AT system but with a different mic. The 830 mic is much better than the 829. The 830mw is actually a pretty good sounding mic. I have a couple of these wireless systems from my starting days and they are actually OK. With a VHF system you will face possible interference amd range and fade out problems. Just make sure you understand the 88W limitations and it works well.

Having said that, I would strongly recommend that the Sennheiser G2 or G3 system should be purchased if you can swing instead. The ME2 mic is not too great, but it's OK.

I have used Pro 88W and Azden WLX PRO's they seem to work in a line of sight in my office but on location they are worthless and have limited reception. I liked the Sennheisers G2's (still had dropouts) before investing in some used high end Lectrosonics.

Basically, if you can't put a minimum of about $600 per channel into your wireless, you're generally better off going hardwired. Add to that the cost of a decent mic.

Buying cheap wireless is a waste of money.