We are on our second Kent Dual-Drive. Both were bought new. We gave the first one away when we moved from NYC to Portland, OR. We had only had it a year. We bought the second as soon as we arrived in PDX. Its going on its seventh year. We pull a sometimes heavily loaded trailer with the Kent and I can definitely feel the frame flex when my stoker (150lb) and the trailer (~100lb) are there. Sudden movement of my stoker or her pedaling do not feel like "flex" to me. I can tell the difference. I don't think a stoker alone creates much flex in a Kent but to be fair a Kent is far from the stiffest tandem out there. I was never able to get the front derailleur on our second Kent to cover all three rings. Rather than replace the derailleur I replaced the bottom bracket with a shorter one. Problem solved. Sadly, I had replaced the index (grip) shifters (with Suntour friction shifters) in an earlier attempt. In hindsight they were probably fine. The bottom brackets are definitely not cassette type sealed BB's and IMO are a worthy upgrade for anyone planning to live long term with one of these bikes. A 'chewed' up FD should definitely be replaced, and they are dead cheap these days. Stock seats are horrible, and the stock seatposts are steel. They will rust. Aluminum ones are available but in 25.4mm they are very fragile unless made of 6060 alloy. So.......
Kent Tandem drop shipped unassembled -- $250. Two sealed BB - $50 . Two Bontrager CRZ Sport saddles $50 (no longer made) One 6061 seatpost (capt) $22 One aluminum seatpost $14. You must be able to work on the bike yourself. If an LBS swaps the BB's, their labor charges are going to kill you. Well maybe not, but all that labor will certainly bring the price of a Kent up to what something like an Electra tandem or Trek tandem is going to cost and that wouldn't be worth it.
After two years we (I) damaged the rims and bought new wheels - $80/
pr. We also bought Schwalbe Big Apples in 2.0" $80.
We have a much nicer tandem ($2K) for club riding that gets out less than 10x/yr. We didn't ride it at all this year. The Kent gets used every single day. Since my wife is blind and we are car free it is the commuter/utility and all around town car. I ride it solo almost as much as two up. Even with all the upgrades the Kent is far cheaper than anything being sold on Craigslist. There are other ultra-cheap dept. store tandems but none are better than the Kent and IMO the Kent is hands down better looking than anything else in its price class. In fact, it gets more admiring comments from the general public than the much nicer one that we use in the summer.