Instinet has survived such threats before, notably in 1975 with the end of fixed brokerage commissions. It boasts a long list of blue-chip clients. It's financially strong. It's growing in multiple ways, abroad and via such new services as bond trading. In a typical IPO, underwriters give their biggest clients first dibs on shares and a large say in the offering price.
Little investors get scraps.
The higher you bid, the more likely you will get them. Yet you also can bid low. Instinet's estimated IPO price is 20 times last year's net. The risk you take is that the deal is priced higher and you get no stock. As IPO risks go, that's one worth running.