If there is anything you have always wanted to see in an exchange, please let us know!
The P2P lending feature is great, but needs some fine tuning. Apparently it is possible to borrow very short term (minutes, hours?) and not pay any interest at all. This feature is being actively abused by some borrowers. Lending offers are taken, and the borrower returns the money immediately. There are various reasons why the borrower would do this. The wildest one being; one could set up a borrowing bot to constantly recycle loans, and thereby borrow without paying any interest at all! For a lender, choosing "Auto-renew" is not always a good option.
Bitfinex solved this same issue by making the borrower pay interest for at least one hour. So even if the borrower returns the money after just 30 seconds, he still pays one hour's worth of interest. This would be a fair way to solve the issue. As per now, lenders gain no interest even though they provide the funds, and Poloniex gains no commission for this activity. If the lender did not have Auto-renew on, his money is now off the market until he comes back (could be days).
---------------------------------------------------------------------
Another suggestion: Currently the site's exchange and lending pages are very slow to use. The site provides you all kinds of unnecessary information, and then immediately starts refreshing that unnecessary data. Getting an offer through, requires sometimes minutes of waiting. For example, when logging in, it is
not necessary to download the full orderbook, chart, market depth, past trades etc. for Monero. That info is needed only by those who trade Monero, not by everyone who logs in. There could be an option to customize what kind of info is shown. E.g., don't want the trollbox? Fine, just opt out in the "My profile"-page. A lot of bandwith and server resources is saved and the site becomes usable again.
The last one: Sometimes after lending with Auto-renew on, the market rate moves up, and there's a need to switch the Auto-renew off for all of one's outstanding loans. This is a pain in the butt, as by that time, your one 10 BTC lending offer has turned into 35 small loans, and you have to click the Auto-renew off one by one. The site is very slow (see the above paragraph), and this will take minutes. So, how about a simple "Auto-renew ON/OFF" switch for "My Active Loans"?