You are making a big mistake. Do NOT spend $150 on a Eris. Dont even spend $100.
The Droid Eris uses an old Arm11 CPU design exactly the same as the original G1 (first android phone from years ago). The hardware was outdated even when the phone was released. It is not powerful enough to run Android smoothly as you can see from all the countless threads of people complaining about how slow the phone is. The other MAJOR issue with the Eris is the low system RAM it has. After the phone boots you only have about 80mb of ram left which is nothing. Slows the phone down alot.
Everyone I know who owns the Eris regrets getting it due to the poor performance. Dont be fooled by how smoothly the home screens slide because when it comes down to actual smartphone use the Eris chokes.