The best of the bunch is the Cybook Opus. It has a 5-inch display and recently got a new firmware update. It comes with 1GB of internal memory and has a microSD card slot. Check our Cybook Opus review for more information about it.
If you’d prefer a larger 6-inch screen, the Astak Mentor is the better choice. Both it and the eSlick share the same hardware design, based on the Netronix EB600. The eSlick was just recently discontinued so don’t expect much from it. Both are outdated models. Newegg is probably trying to clear stock.
For most, spending an extra $40 more for a Kindle WiFi or $50 more for a Nook WiFi would be a much better deal in the long run, given the advanced features and better hardware, but it’s good to see ereaders breaking the $100 barrier nonetheless.