I have the same experience with gnubler. I get their bid requests frequently and rarely even bother to look. I had one experience with them that I will share, not to slam anyone, just to provide my experience as requested by Gino.
We get a bid request (one of the first few I received from them) for an install only for a new ground-up car wash going up a few towns over. I looked at their "suggested price" and almost instantly decided I had no interest. It was probably around 60% of what I would bid. Apparently the same was true for most of the local shops because they emailed a couple times asking if I was going to bid. I finally replied that we rarely do that type of work and suggested a few contacts who might but would be well above their suggested amount. They go away, no big deal...
About two weeks later I got a call from the project lead on a Friday and he is in a rush to get the "Coming Soon" sign moved because the shop they hired not only put it on the wrong lot completely, but installed it in front of a Bank that was still open and in business. I got a laugh but he said the shop they contracted with wouldn't make it back until the middle of the next week and the bank was pissed. I asked how much and he gave me the typical whatever it takes answer and I asked about how and when I would get payed and COI requirements and he basically said "oh we can figure that out later". Yeah, sure, nope. I also asked for him to send the permit for it and he told me "it doesn't need one" which it definitely did (this town requires permits even for temporary signs). I told him I would stop out and mark locates if I had time and he promptly told me that locates were unnecessary and I "should be fine", after all its just a couple 4x4 posts in the ground. At this point, I was well beyond wanting anything to do with these guys.
That sunday I was driving through that town and out of curiosity stopped by the site. All that was left was a single 4x4 post that someone had half attempted to remove sticking out of the banks nicely mowed grass. Just for fun I put a couple white flags up where the sign was originally supposed to go, just a little help for the next guy ha ha. Actually, where they wanted it was about 15 ft closer to the road and beyond the property line and also in the highway right of way, so I moved it back per local code.
Their suggested cost for this temporary sign in the original bid was scarcely more that the cost of the lumber "to be provided by installer".
In general, I get the feeling they are using as cheap of labor as possible with little to no care about quality or longevity of the product. Not something I want my shop associated with. Hope this helps.