Over the years, I've worked in several different office settings. In one office, all of the furniture was brand new; the owner had shelled out a significant amount of money on the items. In another office, everything was used but wholly functional. In a third environment, the items were a mishmash, purchased as we went along and grew.
The truly interesting part? The office with all new furniture was the most challenging to work in. We were constantly adjusting things and modifying them to match our work flow, but at the same time we weren't simply able to get rid of these nice new items that didn't match how we wanted to work. With the old items, we didn't feel bad about simply eliminating the items that didn't match our needs. In the mix-and-match office, which was actually the best for our workflow, we only added items if there was a specific, clear purpose for adding the items.
I learned three things from all of this.
First, new office furniture does not mean increased productivity. In my experience, it often had little impact on productivity at all - any gains made were often offset by the learning curve and the repurposing of equipment that wasn't necessary (like overbearing and annoying keyboard trays). In short, in terms of "bang for the buck" for your business, new furniture isn't the best place to start.
Second, bare-bones furniture often did mean increased productivity. The single most productive desk I've ever owned in my life consisted of four boards nailed together. Why was it so productive? Everything I needed to work was right there on the desk top. I didn't need anything else. When I decided I needed a hole for my cords to go through, I literally took out a drill and drilled it myself. Why? It was four boards nailed together - I didn't feel a need to keep it pristine or perfect. Function trumps form.
Third, you can get surprisingly high-quality used office furniture for a pittance if you look for it. Look for going-out-of-business sales and foreclosure auctions, for starters, as these places often have items that go for very little.
There are two huge advantages that come from starting off with minimal-cost office furniture. First, it minimizes your startup costs - you can focus that money into other areas, such as personnel and equipment. Second, with little invested in the furniture, you can feel much more free to modify, tweak, and upgrade the furniture to your heart's content - or your employee's heart's content.
Even after all these years, I still miss that old desk that was made out of four boards nailed together. It was so simple as to never distract me. It was incredibly easy to modify and I never felt bad about any such modifications. When it finally did give way, I didn't have a significant financial loss, either - I was simply able to move on from it.
Remember this: office furniture is there to enable you to do your work. Your goal is to maximize productivity while minimizing cost. Used furniture basically gives you the freedom to not invest money in the items while also giving your employees the freedom to modify the items as they wish to maximize their productivity. It's a win all around, in my opinion.