Hey,
I've spent a good bit of time doing ERP, but have since moved on. We looked at a few different options and ended up setting on Epicor. Version 9 was rough, but 10 seems to have fixed a lot of what was wrong from the technical side of the house.

The best advice I can give you is to change your business processes to fit the ERP rather than the other way around. Not only are most ERPs designed around best practices, trying to customize (read: bastardize) the system to fit your homegrown business processes leads to a ton of unnecessary cost and pain. Here are the findings in this blog about ERP