Business owning dopers - merchant services

I have recently started up my own business and I am looking into being able to accept credit cards and I have a few questions some polling, some not.

#1 Any places you have had BAD experiences with or have other problems like huge hidden fees or some other such thing that tends to bite you in the butt.

#2 Its onsite computer tech work, would collection of CC info be best handled by:

[ul]
1 The good ole style slider devices
2 Just writing the CC number on the invoice and plugging #'s manually into a terminal at home.
3 Some kind of battery powered CC terminal wireless or one that batches and downloads everything at a later time.
4 Using a merchant account that processes via a web page.
[/ul]

All obviously have their pros and cons, Wireless live systems are out there but are kinda pricey. I’m curious if decline rates on batched transactions posted later would really justify the extra expense of a live process. Average transactions should be in the $100 range so processing fees can add up in a hurry and I know different methods carry different costs.

So I guess I’m looking for experiences in the process and any best practices that have helped you with regard to your CC handling.

Thank you,
Chris