In my opinion, IEO is really just an upgrade of the ICO. So it is really difficult to invest them at a time when the market is going down. They are too dangerous for investors, instead they will choose better options like buying BTC.
Not exactly an upgrade since the method to crowdfund is basically the same. The only difference is IEO held by the popular exchange which will demand some portion of money gathered at the end of the IEO funding phase while they are also giving their popularity and reputation for the project to reach a mass audience. So, IEO is just a fancy name for ICO that is already being reviewed by the exchanges.