Here's my experience so far. (...) they withheld at my marginal tax rate (28%) from the proceeds of the sale (the proceeds not the gain). So they withheld ~$160 from the ~$600 sale. This seems very sketchy. The only way they would know my tax bracket is by the income that I declared on my application form.
Needless to say I was a little miffed about the withholding. I sent a two emails over the course of the next week. Neither received a response. So I phoned them and they informed me that they had not received my paperwork (this was about a month after I had opened the account and mailed in the form). I decided that at that point that I was pretty much done with Zecco. But then I noticed a couple days later in the "Account Overview" section that the "Outstanding Paperwork" field (which previously had been blank), now said "No". So apparently it took them about a month to process the paperwork. I called them up again and they said they had received my paperwork, but they also told me that the ~$160 had already been forwarded to the IRS and I would be unable to get it back. It's not a huge deal, since it's only $160 lost until tax time, but it could have been worse, obviously.
Anyways, I have made a couple more trades since with most of the remaining of my original deposit and have not had any more problems. The trading part of there website is fine.
If you open an account with them just learn from my mistake, don't make any trades until your account says "Outstanding Paperwork: No" no matter how long that takes. And then make a small trade in and out to verify no withholding.
So for me I think it boils down to this:
PROS:
Free trades (really!)
CONS:
Difficult setup.
Inconsistent service.
Questions about long-term viability.