Timba definitely leaves a lot to be desired if you are using it for more than just a quick, one off survey. Even getting it to work properly can be difficult, since it is fairly buggy. For instance, I have to actually inspect the page and remove problematic DOM elements in order to even be able to create a list of survey recipients.
It also is very limiting on how many recipients you can have for a given survey in a couple of ways. The first is that you can't send out more than a certain amount of surveys at once - about 400 in my experience. The second is that there is a limit of around 10,000 total recipients for any given survey before it will not accept any more recipients period. This might be fine for some uses, but it gets eaten up fairly quickly when you're doing high volume ecommerce. All this means that its okay for getting a snapshot of what people think, but it isn't really good for tracking responses over a longer period of time.
The export formats are also lacking if you are trying to track trends over time while still being able to view smaller slices. As soon as you select a date range, you lose the ability to export in any sort of a spreadsheet and are stuck with a PDF.
There are several other minor clunky features that can derail your research, such as needing to turn on survey collection manually each time you create a new survey. It's easy to overlook, and suddenly you are sending out surveys that people aren't able to respond to. You also can't just assign an email template to be used, you have to manually copy and paste the email contents every time you create a new survey.
Finally, the support is basically nonexistent. They have a few things on the Timba site itself, but most issues you will be stuck figuring out yourself.
We use survey tools to do a blend of qualitative and quantitative research on our products. The ratings questions allow us to set a baseline of our user's perception of our products that we can refer back to when trying to quantify the effect of changes to the product , while the open ended questions allow us to get more general feedback on how people feel and what issues we should look into. Responses aren't anonymous unless you specifically set them to be, so you can follow up on answers you want to know more about and set up interviews/ user testing sessions as you see fit.