Out of the three EnGenius routers, the compact ESR-300H made the best impression on us. If you have no use for a router that supports 5 GHz, like if you don't own any devices that are compatible with that frequency, then it's a worthy option. However, its average price of £60 is eerily close to that of a number of quite good dual-band routers from other brands, for example the Edimax BR-6675nD. The VPN server on the ESR-300H could have put that model on top, were it not for the slow 100 Mbit ports.
While the ESR-600H and ESR-750H have gigabit ports, they fall short in terms of performance, especially when you consider their purchase price. If that price can drop significantly, these routers can become interesting. Until then, not even the cool AirPlay feature on the ESR-750H is enough to do that.